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TEXT  BOOK  OF  CHEMISTRY 

FOR 

NURSES  AND  STUDENTS  OP  HOME  ECONOMICS 


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^•iiliiliiililiiiiiiTilmiiWin^ 


TEXT  BOOK  OF  CHEMISTRY 

FOR 

NURSES  AND  STUDENTS 
OF  HOME  ECONOMICS 


BY 
ANNIE  LOUISE  MACLEOD 

ASSOCIATE    PROFESSOR  OF  CHEMISTRY,  VAS8AR  COLLEGE;  ASSISTANT   PROFESSOR, 

NUKBKS   TRAINING  CAMP;    LECTURER  IN  CHEMISTRY,  VASSAB  BBOTBBBS 

HOSPITAL,    POUGHKEEPSIE,    1918-19. 


FIRBT  EDITION 


McGRAW-HILL  BOOK  COMPANY,  INC. 

NEW  YORK:    239  WEST  39TH  STREET 

LONDON:    6  &  8  BOUVERIE  ST.,  E.  C.  4 

1920 


COPYRIGHT,  1920,  BY  THE 
McGRAW-HiLL  BOOK  COMPANY,  INC. 


PREFACE 

The  purpose  of  this  book  is  to  present  in  one  volume 
those  general  principles  of  chemistry,  inorganic,  organic, 
and  physiological,  which  give  the  necessary  foundation  for 
practical  courses  such  as  nutrition,  dietetics  and  cookery, 
materia  medica,  bacteriology,  and  so  forth,  which  are 
more  or  less  directly  dependent  on  a  basis  of  chemical 
theory.  With  this  object  in  view  I  have  eliminated 
much  that  would  be  included  in  the  conventional  chem- 
istry course,  in  order  to  avoid  confusing  the  student  who 
has  only  a  limited  amount  of  time  to  spend  on  this  sub- 
ject. On  the  other  hand  I  have  included  certain  topics 
which  are  not  usually  dealt  with  in  a  course  so  elemen- 
tary in  character  but  which  lead  to  a  fuller  understanding 
of  everyday  phenomena. 

Throughout  the  text  I  have  kept  particularly  in  mind 
the  needs  of  the  nurse-in-training,  since  my  experience 
in  teaching  this  class  of  student  has  led  me  to  believe 
that  they  should  have  a  rather  special  type  of  instruction 
in  chemistry.  In  selecting  my  material  I  have  en- 
deavoured to  conform  to  the  requirements  of  the  Com- 
mittee on  Education  of  the  National  League  of  Nursing 
Education,  and  of  the  New  York  State  Board.  Since, 
however,  these  requirements  are  based  on  a  consideration 
of  those  applications  which  will  be  made  in  the  later 
experience  of  the  nurse,  an  experience  which  has  many 
points  in  common  with  that  of  the  Home  Economist  I 
trust  that  this  text  may  prove  equally  useful  for  students 
of  both  types. 

Inasmuch  as  many,  if  not  most  of  our  hospitals  have 
neither  the  time  nor  the  equipment  necessary  to  include 

v 

434.1 5G 


vi  PREFACE 

laboratory  work  or  even  lecture  demonstration  as  part 
of  the  course  in  chemistry,  I  have  endeavoured  to 
produce  a  text  which  can  be  used  with  profit  without  these 
aids.  Since,  however,  it  is  unquestionably  desirable 
to  introduce  experimental  work  when  possible,  in  order 
that  the  student  may  acquire  dexterity  in  manipulation, 
accuracy  in  observation,  and  neatness  and  despatch  in 
following  directions,  I  have  included  a  practical  manual 
of  experiments,  requiring  only  the  simplest  apparatus, 
which  may  be  used  either  whole  or  in  part  for  laboratory 
work  or  class  demonstration.  The  experiments  marked 
Demonstration  are  a  little  more  elaborate  than  the  others, 
requiring  more  time  or  more  apparatus  than  is  usually 
convenient  to  provide  for  each  member  of  the  class, 
but  they  may  advantageously  be  carried  out  by  the 
instructor  as  illustrations  of  certain  points  taken  up  in 
the  class  work. 

It  is  very  frequently  the  case  that  some  members  of 
a  class  have  already  had  a  course  of  chemistry  in  high 
school.  Such  advanced  students  might  very  well  be 
entrusted  with  the  task  of  carrying  out  the  demonstra- 
tions, preparing  solutions,  etc.,  under  the  supervision  of 
the  instructor,  thus  acquiring  a  little  more  experience 
and  manipulative  skill,  instead  of  repeating  those  experi- 
ments with  which  they  are  already  familiar. 


CONTENTS 

SECTION  I 
INORGANIC  CHEMISTRY 

PAGE 

CHAPTER  I.  INTRODUCTORY , 1 

Elements  and  compounds — Mixtures — Atoms — Molecules — 
Atomic  and  molecular  weights — Symbols — Formulae — Equa- 
tions— Valence. 

CHAPTER  II.     OXYGEN 11 

Occurrence — Properties — Importance  of  oxygen  in  water — 
Oxidation — Combustion — Kindling  point — The  lighting  of  fires 
— Spontaneous  combustion — Why  is  oxidation  accompanied  by 
lise  in  temperature? — Energy — Chemical  energy — Energy  of  life 
processes — Reduction — Reducing  and  oxidizing  agents — Ozone 
— Oxides  of  carbon — Carbon  monoxide — Formation  in  coal  fire 
— Poisonous  character — Carbon  dioxide — Properties — Use  in 
fire  extinguishers — Soda  water — Aerated  waters — Carbonic  acid 
Excretion  of  carbon  dioxide  from  the  body — Test  for  carbon 
dioxide — Production  from  baking  soda — Baking  powders — Cal- 
cium carbonate — Oxides  of  hydrogen — Hydrogen  peroxide. 

CHAPTER  III.  WATER 24 

Water  as  a  reagent — Hydrolysis — Solution — Diffusion — Osmotic 
pressure — Normal  saline — Ringer's  solution — Solubility — Crys- 
tallization— The  setting  of  Plaster-of-Paris — Suspensions — 
Emulsions — Filtration — Colloidal  solutions — The  practical 
applications  of  colloids — Collargol,  a  bactericide — Gelatine  in 
ice-cream — Gruel  eggs,  etc.  in  milk — Why  rivers  are  muddy — 
Use  of  filters  in  purification  of  water — Dyalized  iron  as  an 
antidote  in  arsenic  poisoning — Sewage  farms. 

CHAPTERS  IV.  Acids,  Bases,  and  Salts 35 

Acidity — "Acid"  hydrogen — Acid  ladicles — Salts — Naming  of 
acids  and  salts — Bases,  or  alkalies — -The  hydroxyl  group — 
Neutralization. 

CHAPTER  V.  ELECTROLYTES  AND  IONIZATION 41 

Conductors  and  insulators — Positive  and  negative  electricity — 
Electrolytes — How  is  electricity  carried? — The  ionic  theory — 
"Strong"  acids  and  bases — Ions  in  chemical  reactions — Elec- 
trolytes in  the  life  piocesses — Acids  and  salts  in  the  diet. 

CHAPTER  VI.  Halogens 48 

The  halogen  family — Chlorine — Hypochlorous  acid — Bleaching 
powder — Bromine — Medicinal  use  of  bromides — Iodine — Tinc- 
ture of  iodine. 

vii 


viii  CONTENTS 

PAGE 

CHAPTER  VII.  CATALYSTS  AND  ENZYMES 50 

Catalysts — Enzymes,  or  ferments — Zymogens — Naming  and 
classification  of  enzymes. 

CHAPTER  VIII.  NITROGEN  AND  THE  ATMOSPHERE 53 

Air  a  mixture — Effect  of  animal  and  plant  life  on  the  atmosphere 
— "Bad  air" — The  effect  of  temperature  and  humidity- 
Ventilation. 

CHAPTER  IX.  COMPOUND  OF  NITROGEN 59 

Proteins,  organic  nitrogen  compounds.  How  plants  and  animals 
obtain  their  nitrogen — The  nitrogen  cycle — Inorganic  nitrogen 
compounds — Ammonia — Household  ammonia — Smelling  salts 
— Ammonia  as  a  refrigerating  agent — Nitric  acid. 

CHAPTER  X.  THE  METALS 64 

Metals— Platinum — Gold — Silver — Silver  polishes — "Sterling " 
silver — Iron — Rusting  of  iron — Protection  from  rust — Gal- 
vanized iron — Enamelled  iron — Nickel — Copper — The  action  of 
acids  on  copper — Copper  in  canned  vegetables — Aluminium — 
The  care  of  aluminum — Lead — Why  foods  should  not  be  left  in 
open  cans — Where  lead  pipes  are  unsafe — Alloys. 

SECTION  II 
ORGANIC  CHEMISTRY 

CHAPTER  XI.  HYDROCARBONS 73 

Organic  chemistry — Graphic  formulae — Isomeric  compounds — 
— Saturated  and  unsaturated  compounds — Paraffins — Halogen 
substitution  products —  Chloroform —  lodoform —  Carbona — 
Alkyl  radicles — Homologous  series. 

CHAPTER  XII.  ALCOHOLS  AND  ETHERS 79 

Alcohols — General  character — Methyl  alcohol,  its  use  and 
poisonous  character — Denatured  alcohol — Ethyl  alcohol — Al- 
coholic beverages — Primary,  secondary,  and  tertiary  alcohols 
— Ethers — General  character — Sulphuric  ether,  an  anaesthetic 
— Ether  a  solvent — Preparation  of  the  skin  for  surgical  work. 

CHAPTER  XIII.  ALDEHYDES  AND  KETONES 83 

Oxidation  products  of  alcohols — Carbonyl  group — Aldehydes 
as  reducing  agents — Formaldehyde — Its  uses  as  a  disinfectant. 

CHAPTER    XIV.  ACIDS 86 

The  carboxyl  group — Acetic  acid — Vinegar — Lactic  acid — Tar- 
taric  acid — Cream  of  tartar — Citric  acid — Salts  of  the  organic 
acids. 

CHAPTER  XV.  ESTERS 89 

General  character — Nomenclature — Hydrolysis  of  esters — Fats 
— Soaps — Hard  and  soft  soaps — Why  does  soap  cleanse? — 
The  action  of  soap  in  hard  water — water  softeners. 


CONTENTS  ix 

PAGB 

CHAPTER  XVI.  CARBOHYDRATES 95 

General  character — Sugars — Classification — Monosaccharides 
— Glucose — Disaccharides — Hydrolysis — Polysaccharides — Re- 
actions of  the  carbohydrates — Fehling  solution — Fermentation. 

CHAPTER  XVII.  AROMATIC  COMPOUNDS    .    .    .  • 110 

General  character — The  benzene  ring — Derivatives  of  benzene 
Carbolic  acid. 

CHAPTER  XVIII.  PROTEINS  AND  VIT AMINES 104 

Composition  of  proteins — Hydrolysis — Amino  acids — 
Vitamines. 

SECTION  III 

PHYSIOLOGICAL  CHEMISTRY 

CHAPTER  XIX.  DIGESTION 107 

Digestion — Assimilation — Metabolism — The  food-stuffs — Saliva 
Influences  affecting  the  flow  of  saliva — Constituents  of  saliva 
Function  of  saliva — The  stomach — Influences  affecting  the  flow 
of  gastric  juice — Acidity  of  gastric  juice — Enzymes  present  in 
gastric  juice — Pepsin — Lipase — Rennin — The  coagulation  of 
milk  by  rennin — Contractions  of  the  stomach — Distinction  be-  . 
tween  ease  and  completeness  of  digestion — Absorption  through 
stomach  walls — Intestinal  glands — Pancreas — Enzymes  of  pan- 
creatic juice — Enzymes  of  intestinal  juice — The  liver — Bile — 
Jaundice — Gall  stones — Peristalsis — Bacteria  of  the  intestinal 
tract — Summary. 

CHAPTER  XX.  ASSIMILATION 121 

Assimilation  of  fats — Function  of  fat — Assimilation  of  car- 
bohydrates— Excretion  of  carbohydrates — Glycosuria — Diabetes 
Acidosis — Assimilation  of  amino  acids — Function  of  amino  acids 
— Why  some  forms  of  protein  are  more  valuable  foods  than 
others — Danger  of  excessive  protein  in  the  diet. 

CHAPTER  XXI.  THE  ENERGY  OF  THE  BODY 128 

Transformation  of  energy — The  Calorie — Energy  value  of  food 
— The  calorimeter— Calorimetric  determinations  applied  to 
dietetic  problems. 

CHAPTER  XXII.  THE  BLOOD 131 

Function — Constituents — The  plasma — Serum — Defibrinated 
blood — Clotting  of  blood — The  red  corpuscles — Haemoglobin, 
a  carrier  of  oxygen — Action  of  carbon  monoxide  on  Haemoglobin 
— White  corpuscles — Opsonins — Transference  of  carbon  dioxide. 

CHAPTER  XXIII.  EXCRETIONS  OF  THE  BODY 136 

Excretion  through  the  skin — Feces — Urine — Uric  acid  and  dis- 
orders connected  therewith — The  diet  in  uric  acid  troubles. 


x  CONTENTS 

PAGE 
SECTION  IV 

PRACTICAL  MANUAL 

CHEMICAL  WHICH  REQUIRE  SPECIAL  CARE  IN  HANDLING 141 

GENERAL  DIRECTIONS 143 

LABORATORY  EXERCISES 148 

1.  To  make  a  Wash  bottle. 

2.  To  Estimate  Capacity. 

3.  Formation  of  Compounds  from  Elements. 

4.  Decomposition  of  a  Compound  into  its  Elements. 

5.  Separation  of  a  Mixture  into  its  Components  by  Filtration. 

6.  Distillation  (Demonstration). 

7.  Decoloration  of  a  Liquid  by  Animal  Charcoal  (Demonstration). 

8.  Oxidation.     Gain  in  Weight  when  Substances  are  Oxidised 

(Demonstration. ) 

9.  Production  of  Oxygen  by  Green  Plants  in  Sunlight 
(Demonstration. ) 

10.  Solution. 

11.  Osmosis. 

12.  Study  of  Carbon  Dioxide. 

13.  Study  of  Acids. 

14.  Study  of  Bases. 

15.  Neutralization. 

16.  Catalysts  and  Enzymes  (Demonstration.) 

(a)  Manganese  Dioxide  as  a  Catalyst. 

(6)  Action  of  the  Enzyme  of  Liver  on  Fats. 

(c)  Precipitation  of  an  Enzyme. 

17.  Experiments  on  Fats. 

18.  Preparation  of  Soap. 

19.  Experiments  on  Carbohydrates. 

(a)  Tests  for  Constituents. 

(6)  Fehling  Solution  Test  for  Glucose. 

(c)  Tests  with  Starch. 

(d)  Fermentation. 

(e)  Test  for  Sugar  in  Milk. 

20.  Tests  on  Protein. 

(a)  Tests  for  Constituents. 
(6)  Coagulation. 

21.  Hydrolysis  of  Protein  (Demonstration). 

22.  Experiments  on  Blood  (Demonstration.) 

(a)  Clotting  of  Blood. 
(6)  Defibrination. 

(c)  Reactions  of  Haemoglobin. 

(d)  Laking  of  Blood. 

CHEMICALS  AND  APPARATUS  REQUIRED  FOR  A  CLASS  OF  TEN 

STUDENTS 169 

LIST  OF  THE  ELEMENTS,  THEIR  SYMBOLS,  ATOMIC  WEIGHTS, 

AND  VALENCES  . 174 


TEXTBOOK  OF 

CHEMISTRY  FOR  NURSES 
AND 

STUDENTS  OF  HOME  ECONOMICS 


SECTION  I 
INORGANIC  CHEMISTRY 

CHAPTER  I 
INTRODUCTORY 

In  the  science  of  chemistry  we  study  the  behavior 
of  substances  under  varying  conditions  and  try  to  ascer- 
tain of  what  they  are  composed,  why  they  behave  as 
they  do,  and  whether  there  are  any  general  rules  which 
govern  their  behavior  and  from  which  we  can  foretell 
the  action  of  these  and  other  substances  in  all  circum- 
stances. Many  such  rules  have  been  discovered  and  are 
now  well-established,  and  the  study  of  chemistry  is 
largely  reduced  to  the  learning  of  these  rules  and  of  how 
to  apply  them. 

The  first  important  generalization  which  we  learn 
to  make  is  that  substances  can  be  divided  into  two  groups, 
elements  and  compounds  If  we  take  any  solid  substance 
we  can  by  grinding  reduce  it  to  powder  so  fine  that  the 

l 


2  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

particles  can  no  longer  be  distinguished  by  the  naked 
eye.  If  we  continue  still  further  it  is  possible  to  get 
it  so  fine  that  the  individual  particles  cannot  be  detected 
with  an  ordinary  microscope.  Eventually,  by  special 
methods,  it  is  possible  to  reach  a  point  where  the  separate 
particles  can  no  longer  be  seen  even  with  the  aid  of  the 
ultramicroscope,  the  strongest  microscope  we  have. 
Mechanical  division  can  go  no  further,  and  yet  each  of 
these  minute  particles  has  all  the  properties  of  the  original 
substance  and  they  behave  in  a  mass  exactly  as  did  the 
undivided  whole.  If  we  now  resort  to  chemical  means 
of  separating  our  substance  it  will  be  found  that  some 
substances  can  be  separated  beyond  this  point  into  two  or 
more  different  kinds  of  matter  with  distinct  characteristics 
and  different  properties,  and  which  by  suitable  means 
can  be  made  to  recombine  into  the  original  substance 
again.  Such  substances  are  called  compounds.  Water  is 
a  compound;  it  can  be  separated  by  means  of  electricity 
into  two  gases,  oxygen  and  hydrogen,  and  these,  if  heated 
to  a  sufficiently  high  temperature  will  combine  and  form 
water  again.  Oxygen  and  hydrogen  are  elements.  They 
cannot  be  further  decomposed  by  any  means  in  our 
power.  Of  all  the  infinite  variety  of  substances  of  which 
our  universe  is  made  up  we  know  of  only  about  eighty 
elements;  all  the  rest  are  compounds  of  these  in  different 
proportions. 

The  most  important  of  the  elements  are  carbon,  oxygen, 
hydrogen,  and  nitrogen.  Silicon  indeed  makes  up 
about  a  quarter  of  the  earth's  surface,  but  as  it  plays 
only  a  very  minor  part  in  the  life  processes  it  is  of  little 
interest  save  to  the  geologist.  The  percentage  of  the 
various  elements  present  in  the  human  body  according 
to  a  recent  estimate  is  as  follows:1 

1  Sherman,  Chemistry  of  Food  and  Nutrition,  2nd  ed.  p.  234. 


INORGANIC  CHEMISTRY  3 

Per  cent. 

Oxygen 65 

Carbon 18 

Hydrogen 10 

Nitrogen 3 

Calcium 2 

Phosphorus 1 

Potassium 0 . 35 

Sulphur 0.25 

Sodium 0.15 

Chlorine 0.15 

Magnesium 0 . 05 

Iron , 0 . 004 

Iodine 

Fluorine Very  minute  quantities. 

Silicon 

A  mixture  of  two  substances  differs  from  a  compound 
inasmuch  as  there  is  no  union  between  the  constituents. 
Substances  can  be  mixed  in  any  proportion,  can  be 
separated  again  mechanically,  and  do  not  change  their 
individual  characteristics  with  the  mixing.  Salt  and 
sand  can  be  mixed  together  in  equal  quantifies,  or  half  as 
much  salt  as  sand,  or  twice  as  much  salt  as  sand,  it 
makes  little  difference  which.  The  product  will  behave 
like  salt  and  sand;  it  develops  no  new  properties  of  its 
own.  By  treating  it  with  water,  filtering,  and  letting  the 
water  evaporate  we  get  our  salt  and  our  sand  separate 
again.  Powdered  sulphur  can  be  mixed  with  iron 
filings  giving  a  mixture  from  which  the  iron  and  sulphur 
can  readily  be  separated,  and  in  which  each  substance 
behaves  as  it  would  if  it  were  alone.  If  we  heat  this 
mixture  gently  however  something  happens;  a  bright 
red  glow  spreads  through  the  whole  mass,  lasting  even 
after  the  flame  has  been  removed,  the  separate  particles 
of  iron  and  sulphur  fuse  together  into  a  solid  mass  from 
which  they  cannot  again  be  separated,  and,  most  im- 
portant of  all,  the  product  has  entirely  different  prop- 
erties from  either  of  the  constituents.  The  mixture 
has  been  converted  by  heat  into  a  compound. 


4  CHEMISTEY  FOE  NURSES  AND  STUDENTS 

The  smallest  part  of  an  element  which  can  exist  as  a 
whole  unit  is  called  an  atom  (from  the  Greek  atomnos 
indivisible).  This  conception  goes  back  to  the  early 
days  of  the  world's  thought.  The  old  philosophers  imag- 
ined that  the  atoms  of  all  elements  were  composed  of  the 
same  kind  of  matter,  but  differed  in  size  and  shape, 
hence  showed  different  properties.  Those  substances 
which  are  pleasant  and  attractive  to  our  senses  were 
supposed  to  be  made  up  of  smooth  round  atoms,  while 
unpleasant  substances  were  composed  of  jagged,  irregular 
atoms  which  force  their  passage  roughly  into  our  percep- 
tions. This  view,  with  some  modifications,  held  sway 
more  or  less  until  about  the  beginning  of  the  nineteenth 
century,  when  the  English  chemist  Dalton  propounded 
his  epoch-making  atomic  theory.  So  simple  does  this 
theory  sound  that  it  is  difficult  to  realize  that  only 
after  its  adoption  could  the  development  of  modern 
chemistry  begin. 

According  to  Dalton,  the  atoms  of  any  one  element  are 
alike  in  all  properties  but  differ  from  the  atoms  of  any 
other  element.  A  compound  is  formed  by  the  combina- 
tion of  atoms  of  different  kinds.  The  nature  of  the 
compound  depends  upon  the  number  and  kind  of  atoms 
present,  therefore  the  composition  of  a  compound 
must  be  fixed  and  definite,  unlike  that  of  a  mixture  which 
may  vary.  An  atom  is  indivisible,  cannot  be  broken 
up  into  anything  smaller;  it  is  the  smallest  part  of  an 
element  which  can  take  part  in  a  chemical  action.  The 
smallest  part  of  a  compound,  however,  must  consist  of 
two  or  more  atoms  which  would  be  separated  if  the 
compound  were  decomposed.  The  early  chemists  spoke 
of  atoms  of  elements  and  compounds  alike,  but  this  led  to 
confusion  since  there  were  then  two  kinds  of  atoms,  one 
divisible  and  the  other  indivisible.  The  term  molecule 
(diminutive  of  moly  a  mass)  was  therefore  adopted  for  the 


INORGANIC  CHEMISTRY  5 

smallest  part  into  which  a  compound  can  be  divided 
without  losing  its  individual  character.  A  molecule 
is  the  smallest  combination  of  atoms  which  can  exist 
alone.  Only  in  a  few  exceptional  cases  can  a  single 
atom  exist  by  itself.  Usually  there  axe  two  or  three 
atoms  of  different  kinds  combined,  but  sometimes  we 
find  two  atoms  of  the  same  kind  existing  together.  In 
the  latter  case  we  have  a  molecule,  since  it  is  the  smallest 
combination  of  those  atoms  which  can  exist  alone,  but  a 
molecule  of  an  element,  since  both  atoms  are  of  the 
same  kind. 

The  properties  of  an  atom  are  invariable  and  unchange- 
able, whether  that  atom  is  found  alone  or  in  combination. 
The  widely  different  characters  of  the  innumerable 
substances  which  make  up  the  universe  is  due  to  the 
properties  of  the  various  atoms  involved.  Among  these 
properties  perhaps  the  most  important  is  the  weight  of 
the  atom.  It  is  of  course  impossible  to  separate  and 
weigh  a  single  atom,  but  it  is  possible  to  compare  the 
weights  of  the  different  elements  and  arrange  them  in 
a  series  according  to  their  relative  weights.  For  in- 
stance, an  atom  of  hydrogen  and  an  atom  of  chlorine 
combine  together  to  give  a  molecule  of  the  compound 
hydrochloric  acid.  If  we  take  a  given  weight  of  chlorine 
we  can  form  from  it  a  definite  amount  of  hydrochloric 
acid,  which  can  be  weighed.  The  total  weight  of  the 
hydrochloric  acid  produced  will  be  the  sum  of  the  weights 
of  the  hydrogen  and  the  chlorine  used.  If  we  then  take 
an  equal  weight  of  chlorine  and  combine  it  with  another 
element,  silver,  each  atom  of  chlorine  will  combine  with 
one  atom  of  silver  to  give  a  molecule  of  another  com- 
pound, silver  chloride.  We  would  find  that  the  silver 
chloride  weighed  more  than  the  hydrochloric  acid  pro- 
duced from  the  same  amount  of  chlorine.  If  we  start 
with  36  grams  of  chlorine  in  each  case  we  will  get  144 


6  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

grams  of  silver  chloride  as  compared  with  37  grams  of 
hydrochloric  acid.  The  weight  of  the  chlorine  started 
with  must  have  been  the  sum  of  the  weights  of  all  the 
atoms  of  chlorine  present,  therefore  in  equal  weights 
there  must  have  been  the  same  number  of  atoms,  and 
as  one  atom  of  chlorine  entered  into  the  composition 
of  each  molecule  of  hydrochloric  acid  and  of  each  mole- 
cule of  silver  chloride  the  number  of  molecules  produced 
would  be  the  same  in  each  case.  The  difference  in  the 
weights  of  the  two  products  must  therefore  represent  the 
differences  in  the  weights  of  the  atoms  of  hydrogen  and 
silver,  which  we  express  by  saying  that  the  atom  of 
silver  is  108  times  as  heavy  as  the  atom  of  hydrogen,  or 
has  an  atomic  weight  of  108.  By  somewhat  similar 
experiments  we  find  the  relative  weights  of  the  atoms 
of  every  element.  Hydrogen  is  the  lightest  of  all 
elements,  so  we  describe  the  others  as  being  so  many 
times  as  heavy  as  hydrogen.  The  atomic  weight  of  an 
element  is  the  weight  of  an  atom  of  that  element  com- 
pared with  the  weight  of  a  hydrogen  atom.  The 
molecular  weight  of  a  compound  is  the  weight  of  a  mole- 
cule of  it,  and  is  the  sum  of  the  weights  of  the  atoms 
making  up  the  molecule. 

Instead  of  writing  the  name  of  an  element  in  full  we 
frequently  make  use  of  an  abbreviation.  This  is  usually 
the  first  letter  of  the  name  of  the  element  in  question, 
but  where  two  elements  have  names  beginning  with 
the  same  letter  we  avoid  the  difficulty  either  by  using 
two  letters,  as  Ba  for  barium  and  Bi  for  bismuth,  or  by 
taking  the  first  one  or  two  letters  of  the  latin  name  of 
one  of  them.  So  I  stands  for  iodine,  but  Fe  (from  ferrum) 
for  iron;  S  stands  for  sulphur,  Si  for  silicon,  and  Ag 
(from  argentum)  for  silver.  These  abbreviations  or 
symbols  have  a  further  significance.  They  stand  not 
only  for  the  element  in  general  but  for  one  atom  of  that 


INORGANIC  CHEMISTRY  7 

element,  or  for  a  definite  weight  of  the  element  which  is 
in  exact  proportion  to  the  atomic  weight.  When  we 
wish  to  indicate  more  than  one  atom  we  write  the  proper 
figure  in  front  of  the  symbol,  except  where  the  atoms 
referred  to  form  part  of  a  molecule,  in  which  case  the 
number  is  written  as  a  subscript.  Thus  3O  represents 
three  atoms  of  oxygen,  but  O2  represents  a  molecule  of 
oxygen  made  up  of  two  atoms,  and  202  represents  two 
such  molecules.  It  would  be  incorrect  to  write  04,  as 
that  would  represent  one  molecule  of  oxygen  made  up 
of  four  atoms,  which  does  not  exist. 

As  molecules  are  made  up  of  combinations  of  atoms 
we  can  express  a  molecule  of  a  compound  by  combining 
together  the  symbols  of  the  atoms  which  go  to  make 
it  up.  Such  a  combination  of  symbols  is  called  a,  formula, 
and  represents  one  molecule.  HC1  is  the  formula  for 
hydrochloric  acid  and  indicates  that  this  compound  is 
made  up  of  one  atom  of  hydrogen  and  one  atom  of 
chlorine.  It  also  stands  for  a  definite  weight  which  is 
represented  by  the  molecular  weight  of  the  compound. 
H2O  is  the  formula  for  water,  and  indicates  the  fact, 
which  was  learned  by  experiment,  that  water  is  made 
up  of  hydrogen  and  oxygen  in  the  proportion  of  two 
atoms  of  hydrogen  to  one  of  water. 

With  the  help  of  symbols  and  formulae  we  can  describe 
any  chemical  action  very  concisely  and  accurately  by 
means  of  an  equation.  HC1  =  H  +  Cl  is  a  way  of 
saying  that  a  molecule  of  hydrochloric  acid  will  break  up 
into  an  atom  of  hydrogen  and  an  atom  of  chlorine. 
H  +  Cl  =  HC1  describes  the  reverse  process.  Also, 
since  each  symbol  stands  for  a  definite  weight  of  the 
element  represented,  we  can  use  these  equations  in 
calculating  the  relative  amounts  of  any  substances  in- 
volved in  a  chemical  action.  For  instance,  since  the 
atomic  weight  of  hydrogen  is  one  and  the  atomic  weight 


8  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

of  oxygen  is  sixteen,  we  can  tell  that  if  we  put  two  parts 
by  weight  of  hydrogen  with  sixteen  parts  by  weight  of 
oxygen  we  will  get  eighteen  parts  by  weight  of  water.  If 
we  have  a  larger  proportion  than  this  of  oxygen  it  will 
remain  unacted  upon  unless  we  increase  the  amount  of 
hydrogen  as  well.1 

Besides  its  weight,  another  very  important  property 
of  an  atom  is  its  combining  power.  One  atom  of  chlorine 
will  combine  with  one  atom  of  hydrogen,  but  an  atom  of 
oxygen  combines  with  two  atoms  of  hydrogen  to  form 
water.  Is  there  any  rule  from  which  we  can  learn  how 
the  atoms  will  combine  together  and  which  will  help 
us  in  guessing  at  the  formula  of  different  compounds? 
Every  atom  has  the  power  of  holding  in  combination 
a  certain  number  of  other  atoms,  and  this  power  is  spoken 
of  as  the  valence  of  the  atom.  The  valence  of  any 
element  is  shown  by  the  number  of  hydrogen  atoms  it 
will  combine  with  or  take  the  place  of.  Atoms  or  groups 
of  atoms  which  combine  with  hydrogen  are  said  to  be 
negative,  or  to  have  a  negative  valence,  while  hydrogen 
and  atoms  which  replace  hydrogen  in  a  compound  are 
said  to  be  positive,  or  to  have  a  positive  valence.  A  group 
is  a  combination  of  atoms  which  has  so  strong  an  attrac- 
tion for  each  other  that  they  are  not  readily  separated 
but  pass  through  ordinary  reactions  as  a  unit.  In 
writing  a  formula,  the  atom  or  group  with  a  positive 
valence  is  placed  first  and  the  negative  atom  or  group 
second.  So  we  write  HC1,  never  C1H;  NaCl,  never 
CINa,  etc.  In  a  whole  class  of  compounds,  the  hydro- 
xides (see  page  39),  we  find  the  hydrogen  apparently 

1  We  must  note  carefully  the  distinction  between  parts  by  weight  and 
parts  by  volume.  It  takes  twice  as  much  hydrogen  by  volume  to  combine 
completely  with  a  given  volume  of  oxygen  to  form  water,  but  hydrogen 
is  so  much  lighter  than  oxygen  that  the  one  volume  of  oxygen  will  be 
found  to  weigh  eight  times  as  much  as  the  two  volumes  of  hydrogen,  and 
so  the  weight  relations  given  above  hold  true, 


INORGANIC  CHEMISTRY  9 

in  the  position  of  a  negative  atom,  NaOH,  KOH,  etc. 
This  is  because  in  these  cases  it  forms  part  of  the  so- 
called  hydroxyl  group,  OH,  the  group  as  a  whole  being 
negative  although  it  contains  a  positive  as  well  as  a 
negative  constituent. 

In  forming  a  compound  a  positive  element  combines 
with  a  negative  element  but  two  positive  or  two  negative 
elements  have  no  attraction  for  each  other  and  are 
never  found  directly  combined.  The  valences  may  be 
rather  crudely  regarded  as  so  many  arms  or  hands 
by  which  the  atoms  hold  to  one  another.  A  monovalent 
element  is  one-armed,  a  divalent  one  two-armed,  and  a 
trivalent,  three-armed.  On  paper  these  valences,  or 
arms,  or  bonds  as  they  are  sometimes  called,  may  be 
indicated  by  lines  going  out  from  the  symbol  of  the  atom, 

H  —  ,  0  <,  Fe^-.  A  divalent  atom  can  combine  with  one 
other  divalent  atom,  thus  Mg  <  +  >0  =  Mg<>O 
(MgO),  or  with  two  monovalent  atoms,  thus, 

H 
2H-+ 


but  it  is  impossible  to  have  a  divalent  atom  combined 
with  only  one  monovalent  atom,  because  in  that  case 
one  valence  of  the  divalent  atom  would  be  uncombined 
and  no  atom  can  remain  in  that  condition.  In  the 
hydroxyl  group  the  O  has  two  negative  valences  while 
the  H  has  only  one  positive  valence,  which  leaves  one 
negative  valence  to  combine  with  another  positive  atom. 
In  water  this  second  valence  is  combined  with  another 

/H 
hydrogen,  0(     ,  whereas  in  the  hydroxides  it  is  com- 

bined with  some  other  element,  such  as  sodium  or 
potassium,  or  with  the  monovalent  group  NH4. 

For  the  most  part,  the  valence  of  an  element  is  un- 


10  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

alterable,  but  there  are  a  few  elements  which  change 
their  valence  under  different  conditions,  such  as  mercury 
which  is  sometimes  monovalent  and  sometimes  divalent, 
and  iron  which  is  sometimes  divalent  and  sometimes 
trivalent. 

The  following  table  gives  the  valences  of  a  few  common 
elements  and  groups. 

Monovalent        Divalent  Trivalent 

H  Hg  (Sometimes  monovalent)      Fe  (Sometimes  divalent) 

Na  O  P04 

NH4  SO4  N  (Sometimes  pentavalent) 

OH  CO3 

Cl 

NO3 

Knowing  these  it  is  easy  to  write  the  formulae  of 
compounds  in  which  they  occur,  or,  conversely,  to 
determine  the  valence  of  any  other  element  from  in- 
spection of  the  formulae  of  its  compounds.  For  instance, 
if  we  wish  to  know  the  formulae  of  the  oxide  of  sodium, 
since  sodium  is  monovalent  it  will  take  two  atoms  of  it 
to  combine  with  one  divalent  oxygen,  so  the  formula 
will  be  Na20,  while  the  oxide  of  mercury  may  be  either 
Hg20  or  HgO  according  as  the  mercury  is  mono  or 
divalent.  On  the  other  hand,  from  the  formula  K2S04 
we  conclude  that  the  element  potassium  is  monovalent 
since  two  atoms  of  potassium  are  required  to  combine 
with  one  divalent  S04  group. 


CHAPTER  II 
OXYGEN 

Oxygen  is  the  most  abundant  of  all  elements.  It 
makes  up  about  one-half  of  the  whole  earth,  and  one 
fifth  of  the  air.  It  can  be  obtained  pure  by  various 
means,  either  from  the  air  or  from  some  of  the  various 
compounds  containing  it.  It  is  a  colorless  gas  like 
air  in  appearance  but  a  little  heavier  than  air.  It  is 
slightly  soluble  in  water,  more  so  in  cold  than  in  warm 
water.  When  a  glass  of  water  is  left  standing  in  a  warm 
room  little  bubbles  of  gas  begin  to  separate  out  and  col- 
lect on  the  inside  of  the  glass  (see  page  28).  These 
bubbles  are  mostly  oxygen.  This  property  of  dissolv- 
ing in  water  is  of  practical  importance  because  it  is 
upon  the  presence  of  dissolved  oxygen  in  the  water  that 
all  aquatic  life  depends.  Moreover,  through  the  in- 
strumentality of  the  bacteria,  it  brings  about  the  puri- 
fication of  our  rivers  from  the  enormous  amounts  of 
sewage  deposited  in  them.  In  the  presence  of  sufficient 
oxygen  the  noxious  substances  are  acted  upon  in  such 
a  way  as  to  convert  them  into  something  quite  harmless. 
Chemically,  oxygen  is  very  active.  Even  when  diluted 
with  other  gases  in  the  atmosphere  we  can  see  its  effects. 
The  burning  of  wood,  the  rusting  of  iron,  and  the  drying 
of  paint  are  all  examples  of  the  activity  of  atmospheric 
oxygen.  Some  metals  are  more  susceptible  to  the  action 
of  oxygen  than  others;  iron  is  very  easily  affected,  alumi- 
num scarcely  at  all  at  ordinary  temperatures.  For  this 
reason  aluminum  utensils  are  easily  kept  bright,  while 
iron  rusts  quickly  unless  covered  with  some  kind  of 

11 


12  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

protective  coating,  tin,  zinc,  or  enamel,  in  order  to  pre- 
serve it. 

The  combination  of  oxygen  with  other  substances  is 
known  as  oxidation,  and  compounds  of  oxygen  with  one 
other  element  are  called  oxides.  If  two  atoms  of  oxygen 
are  present  in  the  molecule  it  is  a  dioxide,  if  three  atoms 
of  oxygen  a  trioxide,  and  so  on. 

Oxidation  may  be  slow,  as  when  metals  rust,  or  rapid. 
Very  rapid  oxidation  is  usually  accompanied  by  the 
evolution  of  light  and  heat,  and  is  then  known  as  com- 
bustion. The  name  combustion  is  not  entirely  restricted 
to  oxidation  processes,  being  sometimes  used  to  describe 
any  action  which  goes  on  with  evolution  of  light  and  heat, 
but  all  ordinary  combustion  is  oxidation.  We  are  apt 
to  think  of  burning  as  destruction  of  matter,  but  all 
our  conceptions  of  chemistry  rest  upon  the  fundamental 
principle  that  so  far  as  our  experience  teaches  us  there 
can  be  no  such  thing  as  destruction  of  matter.  Matter 
can  be  made  to  undergo  many  changes,  it  can  be  dis- 
sipated and  so  lost  to  us,  but  we  know  of  no  change  in 
which  the  actual  amount  of  matter  in  the  universe  is 
altered.  We  can  neither  add  to  it  or  take  away  from  it. 
In  burning  the  greater  part  of  the  combustible  material 
is  converted  into  gases  and  so  disappears  from  view,  but 
if  we  burn  a  candle,  for  instance,  in  such  a  way  that  the 
gases  produced  can  be  collected  and  weighed  it  will  be 
found  that  they  actually  weigh  more  than  the  candle 
started  with,  and  this  proves  true  of  every  case  of  com- 
bustion. Combustion  therefore  must  consist  in  adding 
something  to  the  burning  material;  that  that  something 
is  oxygen  can  be  demonstrated  in  either  of  two  ways. 
Sometimes  we  can  decompose  the  product  again  into 
its  elements  as  is  the  case  with  the  oxide  of  mercury. 
Or  we  can  show  that  if  all  the  oxygen  be  removed  from 
the  air  no  combustion  will  take  place. 


INOEGANIC  CHEMISTRY  13 

If  combustion  is  oxidation  and  there  is  a  large  supply 
of  oxygen  present  in  the  air  all  the  time,  why  does  not 
everything  which  is  combustible  burn  up  of  its  own 
accord?  Why,  for  instance,  is  it  necessary  to  use 
matches  and  kindling  wood  to  light  a  fire  which,  once 
started,  will  go  on  burning  till  there  is  no  fuel  left?  For 
all  reactions  there  is  a  certain  temperature  below  which 
the  action  will  not  take  place  or  will  take  place  so  slowly 
as  to  be  imperceptible.  For  combustion  this  temperature 
is  called  the  kindling  point,  and  in  the  case  of  most  sub- 
stances is  well  above  ordinary  temperature.  The  ve- 
locity of  any  reaction  increases  with  rise  in  temperature. 
At  low  temperatures  combustion  goes  on  with  extreme 
slowness,  but  as  the  temperature  is  raised  the  rate  in- 
creases and  as  the  rate  increases  more  and  more  heat  is 
developed  by  the  reaction  itself,  until  this  heat  is  suffi- 
cient to  raise  the  burning  substance  to  incandescence 
and  to  maintain  it  at  a  temperature  above  the  kindling 
point  until  the  whole  is  consumed.  If  we  cool  the  sub- 
stance down  below  this  point  the  burning  stops.  If  we 
place  a  wire  gauze  an  inch  or  so  above  an  unlighted 
gas  jet  from  which  a  stream  of  gas  is  flowing  and  then 
light  the  gas  above  the  gauze  carefully  it  will  burn  above 
the  gauze  without  becoming  ignited  below.  This  is 
because  the  wire  conducts  the  heat  away  so  rapidly  that 
the  gas  below  is  not  heated  to  its  kindling  point.  When 
the  gauze  becomes  hot  however,  as  happens  sooner  or 
later,  the  lower  part  of  the  gas  becomes  heated,  takes 
fire,  and  the  whole  burns.  It  is  because  of  this  property 
of  wire  gauze  of  conducting  away  and  dissipating  heat 
that  miners  can  carry  a  lantern  surrounded  with  such 
gauze  into  a  mine  full  of  inflammable  gases.  The  light 
inside  will  burn  safely  with  out  igniting  the  gas  outside, 
unless  the  gauze  becomes  over-heated,  in  which  case  an 
explosion  occurs.  The  head  of  a  match  is  made  of  some 


14  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

substance  with  a  very  low  kindling  point.  As  it  burns 
it  generates  enough  heat  to  ignite  the  rest  of  the  match 
and  this  generates  still  more  heat.  If  we  apply  a  lighted 
match  to  a  large  piece  of  wood  the  heat  is  conducted 
away  over  the  surface  so  rapidly  that  the  wood  does  not 
take  fire.  In  order  to  make  a  fire,  then,  we  surround  our 
large  sticks  with  thin  bits  of  dry  kindling  which  have  a 
low  kindling  point  and  ignite  these  with  a  match  thus 
generating  enough  heat  in  their  burning  to  maintain  the 
larger  pieces  at  ignition  temperature. 

Some  substances  oxidise  so  rapidly  in  air  at  ordinary 
temperature  that  the  process  becomes  combustion. 
This  is  what  is  known  as  spontaneous  combustion. 
Many  oils,  for  instance  linseed  oil,  absorb  oxygen  very 
rapidly,  giving  a  solid  oxidation  product.  Linseed  oil 
is  used  in  painting  because  it  absorbs  oxygen  and 
forms  a  tough  resinous  skin  which  holds  the  coloring 
matter  in  suspension  and  protects  the  material  under- 
neath from  further  action  of  the  air.  Paint  oils,  there- 
fore, do  not  dry  in  the  ordinary  sense  of  the  word,  by 
evaporation,  but  by  oxidation.  If  rags  greasy  with  oil 
or  heaps  of  greasy  material  be  left  undisturbed  for  some 
time  in  a  badly  ventilated  place  the  heat  developed  by 
the  slow  oxidation  may  raise  the  temperature  high 
enough  for  spontaneous  combustion. 

Why  is  oxidation  accompanied  by  rise  in  temperatures? 
To  answer  this  question  we  must  consider  the  energy 
changes  in  chemical  reactions.  Energy  is  most  simply 
defined  as  ability  to  do  work.  It  exists  in  various 
forms,  mechanical  energy,  heat,  light,  and  electrical 
energy.  These  can  be  transformed  from  one  into  another, 
but  can  never,  by  any  means  of  which  we  know,  be 
either  created  or  destroyed.  When  we  speak,  as  we 
sometimes  do,  of  producing  energy  by  some  means 
or  other  we  mean  simply  that  we  have  changed  it  from  ~a 


INORGANIC  CHEMISTRY  15 

form  in  which  it  was  not  available  for  our  purposes 
to  a  more  useful  form.  For  instance,  we  can  take  the 
mechanical  energy  of  falling  water  and  use  it  to  turn  a 
wheel  which  will  set  a  mill  in  motion,  or  we  can  use  that 
same  energy  to  charge  a  dynamo  and  so  get  it  converted 
into  electrical  energy  which  can  be  transmitted  through  a 
wire  to  a  point  many  miles  away  and  there  be  reconverted 
into  mechanical  energy  again.  All  forms  of  energy  can 
be  converted  into  heat.  When  a  piece  of  iron  is  ham- 
mered it  becomes  hot,  due  to  the  conversion  of  the 
mechanical  energy  of  the  blow  into  heat.  When  a 
current  of  electricity  is  passed  through  a  wire  the  wire 
grows  hot,  due  to  the  transformation  of  a  part  of  the 
electrical  energy  into  heat.  Whence  then  comes  the 
heat  which  appears  when  we  burn  a  candle?  We  are 
not  yet  in  a  position  to  answer  this  question  directly, 
but  a  solution  may  be  arrived  at  from  a  consideration 
of  certain  other  phenomena. 

If  we  pass  a  current  of  electricity  through  water  con- 
taining a  little  acid  the  water  is  separated  into  its  ele- 
ments, hydrogen  and  oxygen,  which  can  be  collected 
separately.  The  electrical  energy  necessary  to  accom- 
plish this  separation  apparently  disappears  completely. 
No  heat,  light,  or  any  other  form  of  energy  that  we  can 
recognize  appears  in  its  place.  But  if  we  put  this  hydro- 
gen and  oxygen  together  and  heat  them  up  to  their 
kindling  point  they  combine  with  a  loud  explosion  to 
form  water  again.  Whence  comes  the  energy  that  mani- 
fests itself  in  the  form  of  a  mechanical  shock  to  our  ear 
drums  which  we  call  a  noise?  Since  it  cannot  have  been 
created  in  the  process  of  combination  it  must  have  been 
present  in  the  elements  and  set  free  from  them  when  they 
combined.  But  in  the  process  of  separating  these 
elements  from  their  compound  in  the  first  place  energy 
was  used  up.  It  seems  a  probable  hypothesis  therefore 


16  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

that  this  apparently  lost  energy  was  really  converted 
into  some  other  form  which  remained  concealed  in  the 
free  elements  until  the  moment  of  recombination.  In 
the  great  majority  of  chemical  changes  heat  is  given  off; 
for  a  few  it  is  necessary  to  supply  heat  or  some  other  form 
of  energy  which  is  used  up  as  the  change  proceeds. 
When  such  heat  appears  in  an  action  of  any  kind  we 
believe  that  it  has  its  source  in  a  kind  of  energy  which  was 
bound  up  in  the  reacting  substances  and  set  free  from 
them  as  a  result  of  the  action  into  which  they  enter. 
This  energy  is  called  chemical  energy.  When  it  is  neces- 
sary to  supply  energy  of  any  kind  in  order  to  keep  an 
action  going  on,  as  in  the  case  of  the  decomposition  of 
water  by  the  electric  current,  we  assume  that  energy  is 
actually  being  transformed  into  chemical  energy.  The 
new  substance  or  substances  formed  must  contain  more 
energy  than  the  substances  started  with,  and  this  energy 
will  reappear  if  we  can  reverse  the  change.  The  heat 
obtained  from  burning  fuel  therefore  comes  from  the 
chemical  energy  set  free  when  the  burning  substance 
combines  with  the  oxygen  of  the  air.  If  the  action  takes 
place  very  slowly  this  heat  may  be  diffused  away  as 
fast  as  it  is  developed,  so  that  it  never  becomes  noticeable, 
as  when  iron  rusts  or  when  hydrogen  and  oxygen  are 
left  in  contact  at  oidinary  temperatures,  but  the  total 
amount  of  heat  produced  is  the  same  whether  the  action 
takes  place  rapidly  or  slowly. 

Whence  comes  the  energy  involved  in  the  life  processes 
of  animals  and  plants?  Plants,  with  the  aid  of  the 
green  coloring  matter,  chlorophyll,  which  they  contain 
are  able  to  utilize  the  energy  of  the  sun  directly.  With 
this  energy  they  decompose  the  compounds  of  oxygen, 
water  and  carbon  dioxide,  which  they  absorb  through 
their  roots  and  leaves.  Some  of  the  oxygen  they  set 
free,  and  the  rest  with  carbon  and  hydrogen  goes  to 


INORGANIC  CHEMISTRY  17 

build  up  their  tissues.  In  this  way  energy  is  stored  up, 
the  energy  of  the  sun  converted  into  chemical  energy 
which  will  become  available  if  these  compounds  can  be 
acted  on  in  such  a  way  as  to  set  free  this  bound  chemical 
energy;  in  other  words,  if  we  can  reverse  the  process 
carried  on  by  the  plants.  This  is  accomplished  by 
oxidising  the  plant  material.  Animals  get  their  energy 
from  this  stored  up  energy  of  plant  substances  which 
is  set  free  by  oxidation  in  the  body,  and  this  oxidation 
is  carried  on  by  the  oxygen  of  the  air  which  is  breathed 
in.  The  oxygen  combines  with  the  hemoglobin  or  red 
colouring  matter  of  the  blood  in  loose  combination  which, 
from  the  ease  with  which  it  breaks  up  again,  is  almost 
more  like  solution  than  combination.  There  is  also  a 
little  oxygen  dissolved  in  the  blood.  This  oxygen  circu- 
lates through  the  tissues  and  there  oxidizes  the  sub- 
stances present  in  the  cells.  The  dissolved  oxygen  is 
used  up  first,  and  as  this  is  used  more  dissociates  from 
the  oxyhemoglobin,  so  that  the  blood  always  contains 
some  free  oxygen  which  the  cells  can  use.  In  these 
oxidation  processes  the  chemical  energy  set  free  is 
converted  into  heat  or  mechanical  energy  which  serve 
to  maintain  the  activity  of  the  living  body. 

In  order  to  have  oxidation  take  place  it  is  not  always 
necessary  to  have  free  or  gaseous  oxygen  present; 
instead  it  may  be  in  the  form  of  some  compound  from 
which  it  may  easily  be  obtained.  For  instance,  if 
water  in  the  form  of  steam  is  passed  over  hot  iron  the 
iron  takes  the  oxygen  from  the  water  forming  iron  oxide 
and  leaving  pure  hydrogen.  The  process  of  taking 
oxygen  from  a  compound  which  contains  it  is  called 
reduction.  Reduction  is  therefore  the  reverse  of  oxida- 
tion, and  the  two  always  go  together.  When  one  sub- 
stance is  oxidized  another  is  reduced.  In  the  experiment 
just  referred  to,  the  iron  is  oxidized  at  the  expense  of 


18  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

the  water  which  is  reduced.  The  life  processes  of  plants 
are  mainly  reduction  processes,  the  corresponding  oxida- 
tions being  secondary,  while  those  of  animals  are  mainly 
oxidations,  the  reductions  taking  the  secondary  place. 

A  substance  which  takes  oxygen  from  other  substances 
is  called  a  reducing  agent,  while  one  that  gives  up  oxygen 
to  other  substances  is  called  an  oxidizing  agent.  Carbon 
and  hydrogen  are  both  good  reducing  agents,  while, 
apart  from  free  oxygen  itself,  nitric  acid  and  its  com- 
pounds are  among  our  best  oxidizing  agents.  Potassium 
nitrate,  or  saltpetre,  is  one  of  the  derivatives  of  nitric 
acid  which  acts  as  an  oxidizing  agent  and  for  this  purpose 
it  is  used,  along  with  carbon  and  sulphur,  in  gun-powder. 
When  the  powder  burns  the  saltpetre  decomposes,  giving 
up  the  greater  part  of  the  oxygen  which  it  contains  to 
oxidize  the  other  substances  present,  with  the  result 
that  a  great  deal  of  energy  is  suddenly  set  free. 

Ozone. — The  molecule  of  oxygen  consists  of  two  atoms, 
but  when  gaseous  oxygen  is  subjected  to  the  action  of 
an  electric  discharge  under  particular  conditions  it 
takes  up  or  absorbs  some  of  the  energy  of  the  discharge 
and  forms  ozone  (from  the  Greek  ozo,  I  smell)  with  three 
atoms  of  oxygen  in  the  molecule.  Since  ozone  contains 
more  energy  than  ordinary  oxygen  it  is  a  more  active 
oxidizing  agent,  and  is  therefore  sometimes  used  for  the 
purification  of  drinking  water,  oxidizing  and  so  destroy- 
ing the  impurities  present.  It  is  also  used  for  the  purifi- 
cation of  air  in  confined  places,  and  various  ozonizers 
designed  for  this  purpose  are  on  the  market.  In  order 
to  make  this  treatment  effective  however  it  would  be 
necessary  to  produce  an  amount  of  ozone  that  would  be 
extremely  unpleasant  if  not  injurious  to  human  beings, 
and  as  ordinarily  used  it  probably  does  more  harm  than 
good  by  merely  disguising  with  its  own  peculiar  pungency 


INORGANIC  CHEMISTRY  19 

the  odours  which  might  otherwise  give  warning  of  a 
tainted  atmosphere. 

Oxides. — The  most  important  oxides  are  the  oxides 
of  carbon  and  of  hydrogen,  each  of  these  elements  form- 
ing two  oxides. 

Carbon  monoxide  is  formed  when  carbon  oxidizes  in 
an  amount  of  oxygen  insufficient  to  convert  it  into 
the  dioxide.  It  is  always  formed  in  a  coal  fire  in  a  stove 
or  furnace,  where  it  may  be  seen  burning  with  a  pale 
blue  flame.  If  the  draft  is  good  it  is  carried  up  to  the 
top  of  the  fire  and  there  meets  more  oxygen  with  which 
it  combines  to  form  the  dioxide,  but  if  the  draft  is  poor 
some  may  escape  either  into  the  room  or  up  the  chimney. 
There  are  two  disadvantages  in  allowing  coal  to  burn 
to  carbon  monoxide  only,  without  further  oxidation. 
In  the  first  place  it  is  very  wasteful.  The  purpose 
of  burning  fuel  is  to  obtain  heat,  and  as  this  heat  is  pro- 
duced from  the  chemical  energy  set  free  when  the  oxygen 
combines  with  the  fuel  it  stands  to  reason  that  the  more 
oxygen  is  combined  with  a  given  amount  of  fuel  the 
more  heat  is  obtained.  Moreover,  carbon  monoxide 
is  a  very  active  poison,  and  therefore  should  not  be 
allowed  to  escape  into  the  atmosphere.  When  taken 
into  the  lungs  it  unites  with  the  hemoglobin  of  the  blood, 
forming  a  bright  cherry  red  compound  which  prevents 
the  hemoglobin  from  performing  its  regular  work  of 
oxidation.  Less  than  one  per  cent,  in  the  atmosphere  is 
sufficient  to  cause  death  when  inhaled,  and  as  little  as 
one-tenth  of  a  per  cent,  is  seriously  injurious.  The 
poisonous  character  of  the  " afterdamp"  found  in  coal 
mines  is  largely  due  to  carbon  monoxide.  Miners  are 
accustomed  to  carry  with  them  a  small  animal  such  as  a 
mouse  or  canary  bird  when  it  is  necessary  to  go  into  a 
part  of  the  mine  which  might  be  supposed  to  contain 
" afterdamp,"  as  these  creatures  are  very  susceptible  to 


20  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

the  gas  and  will  show  its  effects  even  when  present  in 
too  small  amount  to  be  detected  otherwise. 

Carbon  dioxide  is  formed  when  carbon  or  carbon 
monoxide  burns  in  excess  of  oxygen.  It  is  a  colorless 
gas,  very  like  air  or  oxygen  in  appearance,  but  with  one 
striking  difference  in  property.  When  a  lighted  splinter 
or  a  candle  is  inserted  in  a  jar  of  carbon  dioxide  the  flame 
is  immediately  extinguished.  Carbon  dioxide  is  a  non- 
supporter  of  combustion.  This,  in  connection  with  the 
fact  that  it  is  so  heavy  that  it  can  be  poured  from  one 
place  to  another  like  water,  makes  it  useful  as  a  fire 
extinguisher.  Most  of  the  chemical  fire  extinguishers 
on  the  market  contain  carbon  dioxide,  or  else  are  so 
devised  that  carbon  dioxide  is  generated  from  some 
materials  when  the  extinguisher  is  in  use.  The  heavy 
gas  is  poured  on  to  the  base  of  the  flame  and  protects  it 
from  the  action  of  the  oxygen  while  itself  offers  no  fuel 
to  feed  the  fire. 

Carbon  dioxide  is  very  soluble  in  water.  At  ordinary 
temperature  and  pressure  water  dissolves  about  its 
own  volume  of  carbon  dioxide,  but  at  lower  temperatures 
or  under  great  pressure  it  can  be  made  to  dissolve  a 
great  deal  more.  Soda  water  is  water  into  which  carbon 
dioxide  has  been  forced  under  a  pressure  of  60-150 
pounds  per  square  inch.  The  water  is  bottled  up  under 
this  pressure,  and  when  the  pressure  is  withdrawn  by  the 
opening  of  the  bottle  the  gas  escapes,  causing  efferves- 
cence and  frothing.  Carbon  dioxide  is  generated  in  the 
process  of  fermentation,  of  which  more  will  be  said 
hereafter,  so  if  a  fermenting  liquid  is  bottled  up  and  left 
fermenting  pressure  is  developed  and  much  carbon 
dioxide  dissolves.  On  opening  the  bottle  this  escapes 
just  as  in  the  case  of  soda  water.  Aerated  waters  of 
various  kinds  are  weak  solutions  of  various  mineral  salts 
into  which  carbon  dioxide  has  been  forced  in  order  to 


INORGANIC  CHEMISTRY  21 

make  them  more  palatable.  When  carbon  dioxide 
dissolves  in  water  a  portion  of  it  reacts  with  the  water 
to  form  a  compound  H2C03,  carbonic  acid. 

H20  +  C02  =  H2C03. 

This  is  a  very  unstable  compound  and  on  gentle  heating 
it  breaks  up  into  its  constituents,  H2O  and  CO2,  On 
account  of  its  relation  to  this  acid  carbon  dioxide  is 
often  called  carbonic  acid  gas. 

Carbon  dioxide  is  always  present  in  the  air  to  the 
extent  of  about  0.03  per  cent.  It  is  present  in  much 
larger  amount  in  expired  breath,  having  been  produced 
in  the  body  as  a  result  of  the  oxidation  processes,  going 
on  there. 

It  is  very  easy  to  prove  the  presence  of  carbon  dioxide 
in  any  gas.  When  carbon  dioxide,  or  any  gas  containing 
carbon  dioxide,  is  passed  through  clear  lime  water  the 
lime  water  turns  milky,  owing  to  the  formation  in  it  of 
a  very  fine  solid  substance.  Lime  water  is  calcium 
hydroxide,  Ca(OH)2,  and  when  carbon  dioxide  is  brought 
into  contact  with  it  it  reacts,  forming  solid  calcium  car- 
bonate, CaCO3,  the  same  substance  that  is  found  in 
nature  as  limestone  or  marble. 

Ca(OH)2  +  C02  =  CaC03. 

As  no  other  gas  has  this  effect  on  lime  water  the  appear- 
ance of  this  milkiness  is  taken  as  proof  of  the  presence 
of  carbon  dioxide. 

Common  baking  soda  has  the  formula  NaHCO3. 
When  heated  it  gives  off  carbon  dioxide  and  water. 

2NaHC03  =  Na2C03  +  H20  +  CO2. 

This  may  be  used  as  a  method  of  obtaining  carbon  diox- 
ide, or  the  same  result  may  be  attained  by  treating  the 
baking  soda  with  an  acid.  In  that  case  the  reaction  is 
a  little  different. 


22  CHEMISTRY  FOB  NURSES  AND  STUDENTS 

NaHCO3  +  HC1  =  NaCl  +  H2O  +  CO2. 

Baking  powder  is  a  combination  of  baking  soda  with  some 
substance  which  will  react  with  it  in  the  same  way  as 
the  acid  given  above,  producing  carbon  dioxide  all 
through  the  dough  so  that  it  is  made  light  and  spongy. 
Sour  milk,  vinegar,  etc.  are  sometimes  used  with  baking 
soda  to  produce  the  necessary  acid.  It  ( may  be  asked 
why  it  is  necessary  to  use  an  acid  at  all  for  this  purpose, 
since  the  carbon  dioxide  would  be  given  off  by  the  soda 
under  the  influence  of  the  heat  used  in  baking,  even  if 
there  was  no  other  substance  there  to  react  with  it. 
The  objection  to  this  is  that  in  that  case  the  Na2CO3 
which  would  be  left  behind  in  the  food  would  give  it  a 
very  unpleasant  taste.  It  is  necessary,  therefore,  to 
add  something  which  will  form  a  harmless  and  tasteless 
combination  with  the  residue  from  the  soda. 

Calcium  carbonate,  which  has  already  been  referred 
to  as  limestone  or  marble,  behaves  like  baking  soda  on 
heating.  It  gives  off  carbon  dioxide  and  leaves  behind 
calcium  oxide,  sometimes  called  unslaked  or  quick  lime. 

CaC03  =  CaO  +  CO2. 

Calcium  oxide,  though  not  very  soluble,  dissolves  to 
some  extent  in  water,  combining  with  it  to  form  calcium 
hydroxide,  Ca(OH)2,  the  product  being  what  is  known 
as  lime  water. 

CaO  +  H2O  =  Ca(OH)2. 

This,  as  has  already  been  pointed  out,  will  react  with 
carbon  dioxide  to  re-form  calcium  carbonate  again. 

The  Oxides  of  Hydrogen. — The  most  common  oxide 
of  hydrogen  is  water,  H20,  but  under  certain  conditions 
we  can  get  another,  hydrogen  peroxide,  H2O2.  This 
is  somewhat  like  ozone,  inasmuch  as  it  readily  gives  up 
its  second  atom  of  oxygen.  It  is  therefore  an  excellent 


INORGANIC  CHEMISTRY  23 

oxidizing  agent.  Pure  hydrogen  peroxide  is  a  liquid, 
very  much  like  water  in  appearance,  but  so  strong  that 
it  blisters  the  skin  if  dropped  on  it.  The  peroxide  of 
hydrogen  used  for  medicinal  purposes  is  a  solution  of 
3  per  cent,  hydrogen  peroxide  in  water.  On  account  of 
its  oxidizing  action  it  decolorizes  a  great  many  colored 
substances  and  is  much  used  as  a  bleaching  agent  for 
delicate  materials  that  would  be  injured  by  strong  reag- 
ents, and  for  the  same  reason  it  finds  extensive  use  as  a 
disinfectant.  The  advantage  about  its  use  in  both  cases 
is  that  the  only  residue  left  over  from  the  reacting  hydro- 
gen peroxide  is  a  perfectly  harmless  one,  water. 

H202  =  H20  +  0.  , 

The  monoxide  of  hydrogen,  water,  is  so  important  a 
subject  as  to  need  a  chapter  to  itself. 


CHAPTER  III 

WATER 

Water  plays  a  part  in  a  vast  number  of  chemical  re- 
actions, either  as  one  of  the  reacting  substances  or  as  a 
by-product  of  the  reaction  or,  sometimes,  simply  as 
the  medium  in  which  the  action  is  carried  on.  A  re- 
action between  water  and  some  other  substance,  in  which 
the  molecule  of  water  separates  into  H  and  OH  and  the 
other  substance  also  separates  into  two  parts  one  of  which 
combines  with  the  hydrogen  and  the  other  with  the  hy- 
droxyl  to  form  two  new  compounds,  is  called  hydrolysis 
(from  the  Greek  hydor,  water,  and  lysis,  loosening). 
Many  examples  of  this  type  of  reaction  will  be  met  with 
later,  especially  in  connection  with  the  decomposition  of 
the  food  substances  in  digestion. 

Perhaps  the  most  valuable  property  of  water  is  its 
power  of  dissolving  a  great  many  other  substances  and 
so  bringing  them  into  a  condition  in  which  they  are  very 
susceptible  to  reaction.  Every  one  is  familiar  with  the 
phenomenon  of  solution.  Salt,  sugar,  and  other  things 
dissolve  in  water,  i.e.,  the  solid  disappears  and  a  clear 
liquid  is  left  which  may  look  like  pure  water  but  which 
has  taken  on  new  properties,  for  instance,  in  the  cases 
mentioned  has  acquired  a  salt  or  sweet  taste.  What 
actually  takes  place  when  a  substance  dissolves  in  water 
is  somewhat  of  a  puzzle  to  chemists.  There  are  those 
who  think  that  there  is  actual  combination  of  some  kind 
between  the  dissolved  substance  (solute)  and  the  solv- 
ent; others  think  that  molecules  of  the  solvent  merely 
diffuse  among  the  molecules  of  the  solvent  somewhat  as 

24 


INORGANIC  CHEMISTRY  25 

a  group  of  people  might  drift  into  a  crowd  and  there 
become  separated  from  one  another  by  the  pressure  of 
the  people  around  them.  Certainly  if  there  is  combina- 
tion at  all  it  is  not  ordinary  chemical  combination  re- 
sulting in  the  formation  of  a  chemical  compound,  since 
the  proportions  of  a  solution  can  be  altered  without 
altering  the  properties.  It  is  easy  to  show  that  diffu- 
sion does  actually  take  place,  whether  accompanied  by 
combination  or  not.  If  a  colored  substance  is  placed  in 
the  bottom  of  a  glass  and  water  is  added  carefully  and 
the  whole  left  standing  undisturbed  for  a  time  the  col- 
ored substance  will  travel  more  or  less  rapidly  up  through 
the  solution  in  opposition  to  the  force  of  gravity.  This 
diffusion  is  the  result  of  a  tendency  on  the  part  of  the 
molecules  to  equalize  the  concentration  or  strength  of 
the  solution  throughout  by  travelling  from  the  part  of 
the  solution  where  the  concentration  is  high  to  the  part 
where  it  is  low.  The  same  thing  is  seen  if  a  lump  of  sugar 
is  dropped  into  a  cup  of  tea  or  glass  of  lemonade  and 
allowed  to  stand  without  being  stirred.  The  sugar  dis- 
solves and  forms  a  very  concentrated  sweet  layer  at  the 
bottom  which  slowly  makes  its  way  up  through  the  solu- 
tion. If  it  is  left  long  enough  it  will  eventually  become 
uniformly  sweet  all  through,  but  this  takes  a  long  time 
unless  the  process  of  diffusion  be  hastened  by  stirring. 
The  force  with  which  the  molecules  of  a  dissolved  sub- 
stance diffuse  through  the  solution  is  called  osmotic 
pressure.  If  we  put  in  the  path  of  the  moving  particles 
a  partition  through  which  they  cannot  pass  but  through 
which  the  particles  of  the  solvent  can  pass  readily,  the 
particles  of  solute  will  exert  a  pressure  on  the  walls  of  the 
partition  which  can  be  measured.  If  the  solutions  on 
either  side  of  such  a  partition,  which  is  called  semi- 
permeable,  are  of  unequal  concentration  the  two  will 
try  to  equalize  themselves.  Since  this  cannot  be  done 


26  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

by  the  passage  of  the  excess  of  solute  from  one  side  to 
the  other  it  will  be  brought  about  in  the  only  way  pos- 
sible, by  the  passage  of  water  from  the  more  dilute  to  the 
more  concentrated,  and  the  force  with  which  the  water 
flows  in  through  the  partition  will  be  exactly  equal, 
though  opposite  in  direction,  to  the  force  with  which 
molecules  of  solute  attempt  to  pass  out.  Two  solutions 
which  are  exactly  equal  in  concentration,  so  that  there 
is  no  tendency  for  water  or  solute  to  pass  from  one  to  the 
other,  are  said  to  be  isotonic.  If  one  is  more  concentrat- 
ed than  the  other,  the  more  concentrated  is  said  to  be 
hypertonic,  the  less,  hypotonic.  The  cell  wall  of  plant 
and  animal  cells  is  semi-permeable,  so  that  while  water 
and  certain  substances  can  pass  in  or  out  quite  readily 
the  cell  contents  cannot  pass  out.  In  this  way  a  certain 
relation  is  maintained  between  the  cell  sap  and  the  fluid 
which  bathes  the  cell  without.  If  the  external  fluid  be 
greatly  diluted  water  will  enter  the  cell  and  dilute  up 
the  cell  sap,  and  if  this  is  allowed  to  go  on  without  check 
the  cell  will  swell  up  and  eventually  burst.  On  the  other 
hand,  if  the  cell  be  placed  in  a  solution  which  is  more 
concentrated  than  the  cell  contents  water  will  pass  out 
from  the  cell,  and  the  contents  will  shrink  up  and  draw 
away  from  the  wall.  This  shrinkage,  due  to  the  with- 
drawal of  water,  is  called  plasmolysis,  and  the  cell  may 
or  may  not  recover  from  it,  according  to  the  extent  to 
which  it  is  carried. 

The  corpuscles  of  the  blood  are  small  cells  floating  in 
the  plasma  or  fluid  part  of  the  blood,  which  is  a  watery 
solution  of  salts  along  with  certain  other  constituents. 
The  corpuscles  also  contain  a  certain  amount  of  water 
and  salts  and  the  osmotic  pressure  inside  the  corpuscle 
must  be  equal  to  that  of  the  plasma  outside  so  that 
while  the  water  molecules  can  pass  either  into  or  out  of 
the  cell  the  exchange  is  equal  in  the  two  directions  and 


INORGANIC  CHEMISTRY  27 

the  condition  of  the  corpuscle  remains  unchanged.  If 
the  corpuscle  is  placed  in  a  more  concentrated  solution 
it  will  shrink,  owing  to  the  flow  of  water  from  the  inside 
out,  and  if  placed  in  a  solution  which  is  considerably 
more  dilute  and  therefore  has  a  much  lower  osmotic 
pressure  than  the  cell  contents  it  swells  and  finally  rup- 
tures owing  to  the  increased  amount  of  water  which  it 
has  taken  up.  It  is  necessary  therefore  in  injecting  liq- 
uids into  the  circulation  or  in  diluting  blood  outside  the 
body  to  be  careful  to  choose  solutions  which  are  either 
isotonic  or  hypotonic  to  the  blood  plasma.  It  has  been 
found  that  a  solution  of  from 0.7  to  0.9  per  cent  of  sodium 
chloride  has  no  effect  on  the  corpuscles  and  such  a  solu- 
tion is  frequently  used  under  the  name  of  "normal  saline," 
or  "physiological  saline."  While  this  is  satisfactory  for 
most  purposes  it  does  not  bear  any  resemblance  to  blood 
plasma  except  in  regard  to  the  osmotic  pressure  since  the 
plasma  contains  compounds  of  calcium,  magnesium, 
potassium,  etc.,  in  addition  to  sodium.  For  this  reason 
a  preparation  known  as  "Ringer's  solution"  is  preferable 
to  normal  saline  for  certain  purposes  since  it  contains 
small  amounts  of  calcium  and  potassium  chlorides  in 
addition  to  sodium  chloride. 

When  a  substance  will  not  dissolve  in  a  solvent  we  say 
that  it  is  insokible  in  that  particular  solvent,  but  between 
very  soluble  and  absolutely  insoluble  substances  there  is 
a  long  range.  The  solubility  of  a  substance  in  a  given 
solvent  depends  partly  on  the  nature  of  the  solvent,  and 
partly  on  the  nature  of  the  substance,  and  partly  on  the 
temperature  employed.  Some  substances  are  almost 
insoluble  in  cold  water,  but  readily  soluble  in  hot. 
The  majority  of  substances  are  more  soluble  at  higher 
temperatures,  but  some,  like  sodium  chloride,  are  very 
little  affected  by  change  in  temperature,  and  a  few,  like 
calcium  hydroxide,  are  more  soluble  at  low  than  at  high 


28  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

temperatures.  Gases  belong  in  this  latter  class;  hence 
the  little  bubbles  formed  on  the  inside  of  a  glass  of  water 
which  has  stood  in  a  warm  room.  The  gases  dissolved 
in  the  water  at  a  lower  temperature  separate  out  as  the 
temperature  rises.  For  every  temperature  there  is  a 
maximum  amount  of  any  substance  that  will  dissolve 
in  any  given  solvent  at  that  temperature. 

When  it  is  desired  to  get  a  substance  into  solution  it 
is  best  to  powder  it  as  finely  as  possible  in  order  that  there 
may  be  as  much  surface  as  possible  for  the  solvent  to  act 
upon;  to  stir  in  order  to  keep  fresh  portions  of  the  solvent 
in  contact  with  the  dissolving  substance  continually; 
and,  if  necessary,  heat.  A  solution  which  contains  as 
much  as  it  can  hold  of  a  solute  is  said  to  be  saturated 
with  that  solute.  If  more  solid  is  added  to  a  saturated 
solution  ftothing  happens.  If  you  saturate  a  solution 
with  a  solute  at  a  high  temperature  and  then  cool  it  down 
to  a  lower  temperature,  some  of  the  solute  will  separate 
out,  because  the  solvent  cannot  hold  in  solution  as  much 
solid  at  the  lower  temperature  as  it  could  at  the  higher. 
Or,  if  a  solution  is  saturated  and  some  of  the  solvent  is 
then  removed  by  evaporation  solid  will  separate  out, 
usually,  if  the  evaporation  has  been  carefully  carried 
out,  in  crystalline  form.  In  a  crystalline  solid  the  par- 
ticles are  arranged  in  definite  geometrical  form  bounded 
by  plane  surfaces.  When  heated,  crystalline  substances 
melt  at  a  definite  temperature,  unlike  amorphous  (non- 
crystalline)  substances,  which  melt  gradually  while 
the  temperature  rises. 

Many  substances  in  the  process  of  crystallization 
combine  with  one  or  more  molecules  of  water.  These 
compounds  are  comparatively  unstable,  losing  this  water 
readily,  and  with  it  losing  their  crystalline  form,  although 
their  properties  otherwise  remain  unchanged.  For  this 
reason  such  combined  water  is  called  water  of  crystalliza- 


INORGANIC  CHEMISTRY  29 

tion.  Ordinary  gypsum,  calcium  sulphate,  crystallizes 
with  two  molecules  of  water  of  crystallization,  the  for- 
mula being  written  thus,  CaSO4.2H2O,  to  show  that  the 
water  is  not  an  essential  part  of  the  compound.  On 
heating  it  loses  nearly  all  of  this  water,  forming  the  white 
powder  known  as  "  Plaster-of -Paris, "  with  the  formula 
(CaS04)2.H2O.  When  this  is  mixed  with  water  it 
readily  takes  up  water  again,  crystallizing  in  minute 
crystals  which  are  interlaced  into  a  firm  rigid  mass 
which  expands  slightly  as  crystallization  proceeds. 
If  the  wet  mixture  is  poured  into  a  mold  and  allowed  to 
"set"  it  will  be  found  to  have  completely  filled  all  the 
crevices  of  the  mold,  giving  a  very  sharp  clear  outline 
when  the  mold  is  removed.  Plaster-of-Paris  finds 
extended  use  in  the  making  of  surgical  casts.  When 
using  it  for  this  purpose  it  is  important  to  remember  that 
expansion  accompanies  crystallization,  as  a  cast  which 
when  wet  fits  quite  comfortably  may  expand  and  there- 
fore tighten  during  setting  to  such  an  extent  as  to 
seriously  impede  circulation. 

If  we  shake  up  an  insoluble  substance  like  sand  with 
water  it  quickly  settles  down  to  the  bottom  again.  The 
finer  we  grind  the  solid  the  longer  it  takes  to  settle,  and 
if  we  have  a  very  finely  divided  solid  it  may  remain 
suspended  in  the  liquid  for  hours  or  even  days  before 
it  settles.  Such  a  mixture  of  fine  solid  particles  sus- 
pended in  a  liquid  is  called  a  suspension. 

A  suspension  of  fine  droplets  of  one  liquid  in  another 
in  which  it  is  insoluble  is  called  an  emulsion.  If  a  liquid 
fat  like  olive  oil  is  shaken  very  hard  with  water  it  forms 
an  emulsion  for  a  few  moments,  but  as  soon  as  the  shak- 
ing is  stopped  the  fat  begins  to  separate  from  the  water 
and  very  soon  the  two  layers  are  perfectly  distinct 
again.  If  a  little  sodium  carbonate,  soap,  or  certain 
other  substances  are  dissolved  in  the  water,  however, 


30  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

the  fat  becomes  so  finely  divided  on  shaking  that  the 
separate  drops  are  indistinguishable  and  the  whole 
liquid  takes  on  a  milky  appearance.  An  emulsion  made 
in  this  way  will  remain  for  weeks,  months,  or  even 
years  without  separating  into  layers,  and  is  called  a 
permanent  emulsion  as  distinguished  from  a  temporary 
emulsion  which  quickly  separates  into  its  components. 
Milk  may  be  called  a  permanent  emulsion  although  the 
greater  part  of  the  fat  rises  slowly  to  the  top  when  the 
milk  is  left  undisturbed.  An  emulsion  of  cod-liver  oil 
is  sometimes  used  medicinally,  and  the  emulsification 
of  the  fats  of  the  food  by  the  bile  is  of  importance  in 
digestion. 

The  process  of  distillation  is  frequently  resorted  to  as 
a  method  of  separating  pure  water  from  other  substances 
which  may  be  dissolved  or  suspended  in  it.  If  water  is 
heated  to  100°  it  is  converted  into  steam,  and  if  this 
steam  is  passed  over  a  cold  surface  it  condenses  to  water 
again.  The  flask,  or  " .still,"  in  which  the  water  is 
boiled  is  connected  with  a  condenser,  or  tube  surrounded 
by  a  larger  outer  tube  through  which  a  current  of  cold 
water  circulates.  By  this  means  the  inner  tube  is  kept 
cold  enough  to  condense  the  steam  and  the  resulting 
"distilled  water"  runs  down  through  the  tube  and  out  at 
the  end.  Any  solid  material  which  was  dissolved  or 
suspended  in  the  water  will  remain  behind  in  the  still. 
It  is  possible  in  the  same  way  to  separate  more  or  less 
completely  two  liquids  whose  boiling  points  do  not  lie 
too  close  together,  and  the  process  of  distillation  is  a 
common  method  of  purifying  other  liquids  besides 
water.  The  distilling  of  whiskey  consists  in  boiling  off 
and  condensing  a  mixture  of  alcohol  and  water,  along 
with  a  small  quantity  of  volatile  flavoring  material.  In 
fractional  distillation  a  mixture  of  two  or  more  liquids  is 
distilled;  as  the  more  volatile  liquid  boils  off  the  tern- 


INORGANIC  CHEMISTRY  31 

perature  of  the  vapor  gradually  rises,  and  by  collecting 
the  product  (the  " distillate")  in  separate  portions  or 
fractions,  according  to  the  temperatures  at  which  they 
come  off,  the  constituents  are  separated.  An  excellent 
example  of  this  is  seen  in  the  distillation  of  petroleum, 
where  crude  oil  from  the  oil  wells  is  separated  into  many 
different  fractions  of  quite  distinct  character,  such  as 
gasoline,  kerosene  (or  coal  oil),  lubricating  oils,  and 
so  on.  Destructive  distillation  consists  in  heating  an 
organic  substance  to  its  decomposition  point  out  of  con- 
tact with  air  so  that  oxidation  may  not  take  place. 
The  gaseous  and  liquid  products  of  decomposition  distil 
off,  and  the  solids  remain  in  the  still.  Evaporation 
differs  from  distillation  in  that  in  evaporation  the  volatile 
vapors  are  allowed  to  escape  and  the  non-volatile 
residue  is  preserved. 

A  suspension  of  insoluble  material  can  be  separated 
into  solid  and  liquid  by  filtration,  that  is  by  pouring  it 
carefully  through  filter-paper  in  a  funnel.  The  liquid 
will  pass  through  the  pores  of  the  paper,  while  the  solid 
is  retained  by  it.  If  the  suspended  material  is  very  fine 
it  will  sometimes  run  through  the  filter  with  the  liquid, 
but  this  difficulty  can  usually  be  overcome  by  heating 
the  suspension  for  a  time.  The  heat  causes  the  small 
particles  to  clump  together  into  larger  lumps  which  can 
then  be  filtered  out. 

Intermediate  between  suspensions  on  the  one  hand 
and  true  solutions  on  the  other  are  colloidal  solutions. 
A  colloidal  solution  resembles  a  true  solution  in  appear- 
ance and  in  the  ease  with  which  it  passes  through  filter 
paper,  but  it  can  be  demonstrated  that  it  is  in  reality  a 
suspension  of  particles  so  fine  as  to  approach  in  some 
cases  molecular  dimensions.  Although  these  particles 
are  quite  invisible  to  the  eye,  even  with  the  aid  of  an 
ordinary  microscope,  they  can  be  detected  by  means  of 


32  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

the  ultramicroscope.  Substances  which  give  true  solu- 
tions with  water,  crystallize  from  water  in  definite 
crystalline  form,  and  when  dissolved  in  water  pass 
through  animal  or  vegetable  membranes,  are  known  as 
crystalloids;  while  substances  which  give  colloidal  solu- 
tions with  water,  separate  in  amorphous  state  and  are 
unable  to  pass  through  animal  or  vegetable  membranes, 
are  called  colloids.  It  is  a  well  known  fact,  however, 
that  substances  which  are  normally  crystalloids  can  at 
times  act  like  colloids,  while  some  colloids  have  been 
obtained  in  crystalline  form.  It  is  therefore  more 
correct  to  speak  of  substances  in  the  colloidal  state 
rather  than  of  colloids  as  a  definite  class,  although  the 
latter  term  is  in  general  use  and  may  be  permissible  if 
used  with  full  understanding  of  its  significance. 

While  some  colloidal  substances,  such  as  very  finely 
divided  metals  and  certain  metallic  compounds,  re- 
semble very  fine  suspensions,  others,  such  as  glue,  gela- 
tine, etc.,  are  more  closely  related  to  emulsions;  they 
are  therefore  classed  as  suspensoids  and  emulsoids 
respectively.  These  two  classes  of  colloids  differ  in 
several  respects.  Suspensoids  show  a  strong  tendency 
toward  coagulation  or  clumping  together  of  their 
particles,  so  that  they  may  quite  easily  be  induced  to 
precipitate  in  an  insoluble  mass;  emulsoids  on  the  other 
hand  have  very  little  of  such  tendency.  They  can  be 
separated  from  solution  (as  happens  in  the  setting  of 
glue,  jelly,  etc.)  but  readily  redissolve  on  the  addition 
of  water.  Suspensoids  are  very  sensitive  to  the  in- 
fluence of  small  quantities  of  substances  of  the  nature 
of  common  salt,  which  cause  them  to  precipitate  from 
solution;  emulsoids  are  not  only  not  precipitated  them- 
selves, but  by  their  presence  are  able  to  protect  suspen- 
soids from  precipitation.  It  is  therefore  possible  by 
the  addition  of  gelatine,  for  example,  to  render  a  sus- 


INOKGANIC  CHEMISTBY  33 

pensoid  so  stable  that  it  can  be  evaporated  to  dryness 
and  redissolved  again  like  an  emulsoid.  Advantage  is 
taken  of  this  fact  in  the  preparation  of  collargol,  a  power- 
ful bactericide.  A  colloidal  solution  of  silver  (suspen- 
soid)  has  sufficient  emulsoid  added  to  prevent  its 
coagulation.  The  water  is  then  evaporated  away,  leav- 
ing the  metal  as  a  fine  powder  which  on  the  addition  of 
water  passes  into  solution  again.  The  effect  of  gelatine 
in  ice-cream  depends  on  the  same  principle.  Com- 
paratively small  quantities  impart  to  the  ice-cream  a 
smooth  velvety  texture  instead  of  the  usual  sandy  grain. 
This  is  due  to  the  protective  action  of  the  emulsoid 
gelatine  preventing  coagulation  of  the  casein  of  the  milk 
into  large  lumps.  For  the  same  reason  small  quantities 
of  gelatine,  gruel,  and  so  on  are  sometimes  added  to  the 
milk  for  babies  or  invalids  with  weak  digestion.  By  this 
means  the  formation  of  a  coarse  curd  in  the  stomach  is 
prevented,  and  it  has  been  found  by  experiment  that 
milk  with  this  addition  is  better  assimilated  than  it 
would  otherwise  be.  In  somewhat  the  same  way  gum 
arabic  when  added  to  candy  prevents  the  crystallization  of 
the  sugar  and  gives  a  product  with  a  soft,  smooth  texture. 
A  suspension  of  finely  divided  clay  behaves  like  a 
suspensoid,  inasmuch  as  the  rapidity  with  which  it 
settles  down  depends  on  the  presence  or  absence  of  salts 
and  emulsoid  material  in  the  water  in  which  it  is  sus- 
pended. The  organic  matter  of  the  soil,  known  as 
"  humus, "  is  emulsoid  and  therefore  the  water  of  rivers 
draining  through  land  rich  in  humus  is  always  muddy. 
Sewage  is  rich  in  colloidal  material  and  a  clear  sparkling 
river  soon  becomes  muddy  if  sewage  is  discharged  into 
it  in  any  quantity.  When  such  muddy  rivers  reach  the 
sea  the  suspended  clay  is  precipitated  by  the  salt  of  the 
sea  water,  resulting  in  the  gradual  filling  up  of  the  river 
mouth. 


34  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

There  is  always  a  certain  amount  of  attraction  between 
two  surfaces  which  are  brought  into  very  close  contact, 
especially  between  a  liquid  and  a  solid.  This  is  illus- 
trated by  the  slowness  with  which  the  last  drops  of  a 
liquid  will  drain  out  of  a  dish.  The  greater  the  amount 
of  surface  exposed  the  stronger  the  attraction.  Every 
housekeeper  knows  that  it  is  wasteful  to  put  a  small 
amount  of  cream,  for  instance,  in  a  large  pitcher  because 
so  much  of  it  will  stick  to  the  surface  of  the  pitcher.  If 
the  pitcher  were  half  filled  with  small  stones  still  less 
of  the  cream  could  be  drained  out,  and  the  smaller  the 
stones  the  more  cream  would  stick  to  them.  Colloids, 
which  have  an  enormous  amount  of  surface  exposed 
in  proportion  to  the  amount  of  material,  and  porous 
substances  like  charcoal,  have  a  great  attraction  for 
certain  kinds  of  dissolved  and  suspended  substances,  and 
this  property  finds  many  practical  applications.  The 
use  of  charcoal  in  filters  for  purifying  water  depends  on 
the  power  of  the  charcoal  of  absorbing  and  retaining  all 
the  impurities  of  the  water.  The  use  of  colloidal  ferric 
hydroxide,  the  so-called  "dyalized  iron,"  as  an  antidote 
in  arsenic  poisoning  depends  on  the  fact  that  the  iron 
collects  the  arsenic  on  its  surface  and  carries  it  out  of  the 
system.  More  important  still,  it  is  to  the  colloids  in  the 
soil  that  the  latter  owes  its  astonishing  power  of  purifying 
the  water  which  drains  through  it.  The  most  remark- 
able illustration  of  this  power  is  seen  in  the  sewage 
farms,  where  the  sewage  is  pumped  out  onto  the  land 
and  allowed  to  filter  through  the  soil  which  retains  and 
is  enriched  by  the  organic  matter  while  the  water  which 
drains  away  is  so  pure  that  it  could  be  drunk  with 
safety.  H 


CHAPTER  IV 
ACIDS,  BASES,  AND  SALTS 

We  are  all  familiar  with  the  general  property  of  acidity. 
This  property  is  peculiar  to  a  large  group  of  chemical 
substances  known  as  acids,  or  to  substances  containing 
these  acids,  and  is  generally  associated  with  a  sour  taste. 
When  we  say  a  fruit  is  very  acid  we  mean  that  it  is  very 
sour,  and  we  call  candies  strongly  flavored  with  lemon 
or  lime-juice  "acid  drops."  There  are  however  other 
properties  besides  this  sourness  which  are  equally  char- 
acteristic of  acids.  One,  which  makes  it  possible  to 
detect  their  presence  without  resorting  to  taste,  is  .the 
power  of  changing  the  color  of  a  vegetable  dye  called 
litmus  from  its  neutral  shade  of  mauve  to  a  bright  red. 
They  all  contain  hydrogen,  and  when  their  solution  in 
water  is  treated  with  a  metal  such  as  iron  or  zinc  hydro- 
gen gas  is  produced.  On  evaporating  the  solution  after 
the  evolution  of  gas  has  ceased  a  new  compound  called 
a  salt1  is  obtained,  in  which  the  metal  has  taken  the  place 
of  the  hydrogen  set  free.  So  invariably  is  this  true  that 
we  derive  the  following  definitions  from  this  reaction. 

An  acid  is  a  substance  containing  one  or  more  atoms 
of  hydrogen  which  can  be  replaced  by  a  metal. 

A  metal  is  a  substance  which  can  replace  hydrogen  in  an 
acid. 

A  salt  is  the  compound  formed  when  the  hydrogen  of 
an  acid  is  replaced  by  a  metal. 

1  "Salt"  as  popularly  used  refers  to  sodium  chloride,  NaCl,  also  called 
table  salt  or  common  salt,  since  it  is  by  far  the  best  known  and  most 
widely  used  member  of  this  class  of  compounds. 

35 


36  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

The  names  and  formulae  of  a  few  typical  examples  of 
each  class  follow: 

Acids  Metals  Salts 

HC1,  Hydrochloric  acid.Na,  Sodium.         NaCl,  Sodium  chloride. 
HNO3,  Nitric  acid          K,  potassium.       CaSO4,  Calcium  sulphate. 
H2SO4,  Sulphuric  acid.  Ca,  Calcium.        Na2SO4,  Sodium  sulphate. 
H2CO3,  Carbonic  acid.   Mg,  Magnesium. Fe(NO3)2,  Ferrous  nitrate. 
H;jPO4,  Phosphoric  acid.Fe,  Iron.  FeCl3,  Ferric  chloride. 

Ca3(P04)2,  Calcium  phosphate. 

Some  acids  contain  a  large  amount  of  hydrogen,  not 
all  of  which  can  be  replaced  by  a  metal  e.g.  C6H8O7, 
citric  acid,  the  acid  present  in  orange  and  lemon  juice, 
of  which  only  three  hydrogens  can  be  replaced  by  metals, 
the  other  five  remaining  unchanged.  Other  compounds 
rich  in  hydrogen,  such  as  turpentine,  Ci0Hi6,  have  no 
hydrogen  that  can  be  so  replaced,  and  such  compounds 
have  neither  a  sour  taste  nor  the  power  of  turning  litmus 
red.  There  must  therefore  be  some  fundamental  dis- 
tinction between  acid  hydrogen  and  other  hydrogen. 
Before  we  can  attempt  to  determine  the  nature  of  this 
difference  however,  we  must  become  familiar  with  one 
or  two  other  types  of  compounds,  of  which  we  will  first 
consider  the  salts. 

As  may  be  seen  from  the  formulae  given  above,  salts 
are  composed  of  a  metal  and  all  of  an  acid  except  the 
acid  hydrogen.  The  residue  of  the  acid,  apart  from  the 
acid  hydrogen,  is  ailed  the  acid  radicle.  It  cannot  exist 
alone  in  the  free  state,  but  it  passes  unchanged  from  one 
compound  to  another  in  the  course  of  reaction.  An 
alternate  definition  to  that  given  above  for  a  salt  is 
therefore:  A  compound  of  a  metal  with  an  acid  radicle. 
The  formulae  of  both  acids  and  salts  are  always  written 
so  as  to  indicate  clearly  what  acid  radicle  they  contain, 
e.g.,  HN03,'  Ca(NO3)2,  (rather  than  CaN2O6),  H2SO4, 
Fe2(SO4)3  (rather  than  Fe2S3Oi2),  and  usually  HsCeHsOT 
in  preference  to  C6H8O7. 


INORGANIC  CHEMISTRY  37 

In  naming  the  acids  and  salts  it  is  desirable  that  the 
names  should  indicate  the  composition  of  the  compound. 
The  names  of  the  commonest  acids  are  made  by  adding 
the  termination  —  ic  to  the  name  of  the  most  characteristic 
element  which  it  contains.  H^SO^  sulphuric  acid. 
H2C03,  carbonic  acid.  HN03,  nitric  acid  (instead  of 
the  more  awkward  word  nitrogenic).  H3PO4,  phos- 
phoric acid  (instead  of  phosphorusic) .  HC103,  chloric 
acid  (instead  of  chlorinic).  Where  we  have  two  or  more 
acids  differing  only  in  the  amount  of  oxygen  in  the  acid 
radicle  the  following  rules  for  naming  have  been  adopted. 
An  acid  exactly  corresponding  to  an  —  ic  aeid,  but  con- 
taining an  atom  of  oxygen  less  in  the  molecule  has  its 
name  ending  in  —  ouSj  H2SO3,  sulphurous  acid;  HC102, 
chlorous  acid,  and  so  on.  If  it  contains  still  less  oxygen 
than  an  —  ous  acid  the  prefix  hypo-  is  attached  to  the  -ous 
name.  HC1O  is  hypochlorous  acid.  If  it  contains  no 
oxygen  at  all  the  prefix  hydro-  is  attached  to  the  ic 
name,  e.g.,  HC1,  hydrochloric  acid,  HBr,  hydrobromic 
acid.  On  the  other  hand,  if  it  contains  more  oxygen  than 
the  -ic  acid  this  is  indicated  by  prefixing  per-  to  the  name 
of  the  -ic  acid,  HC1O4  is  perchloric  acid. 

Salts  are  named  from  the  acids  from  which  they  are 
formed.  Salts  of  -ic  acids  have  the  ending  -ate  substi- 
tuted for  -ic\  for  instance,  the  salts  of  nitric  acid  are 
called  nitrates.  Salts  of  -ous  acids  have  the  ending  -ite 
substituted  for  -ous]  the  salts  of  nitrous  acid  being  ac- 
cordingly called  nitrites.  Salts  of  hydro-acids  have  names 
ending  in  -ide.  In  a  few  cases,  of  which  the  salts  of 
sulphuric  and  phosphoric  acids  are  the  most  important, 
the  characteristic  endings  are  attached  to  the  first  syl- 
lable of  the  name  of  the  acid.  So  we  speak  of  sulphates 
and  sulphites,  phosphates  and  phosphites,  instead  of 
sulphurates,  phosphorates,  and  so  on.  When  we  wish 
to  indicate  the  salt  of  some  particular  metal  the  name  of 


38  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

the  metal  is  placed  first,  the  name  representing  the  acid 
radicle  second;  NaCI,  sodium  chloride,  K2SO4,  potassium 
sulphate.  In  the  case  of  metals  like  mercury  and  iron 
which  can  exist  with  higher  or  lower  valences  this  is 
indicated  by  the  terminations  -ous  and  ic  attached  to  the 
name  of  the  metal ;  HgCl,  in  which  the  mercury  is  mono- 
valent,  is  mercurous  chloride,  while  HgCl2,  in  which  the 
mercury  is  divalent,  is  mercuric  chloride.  Iron  may  be 
either  di-  or  tri-  valent,  so  FeCl2  is  ferrous  chloride,  and 
FeCl3  is  ferric  chloride,  and  similarly  for  the  whole  series 
of  salts  of  both  metals. 

In  the  formation  of  salts  sometimes  only  a  part  of  the 
acid  hydrogen  is  replaced  by  the  metal.  Such  salts, 
which  still  contain  one  or  more  atoms  of  acid  hydrogen 
are  called  acid  salts,  or  have  the  prefix  bi-  attached  to  the 
name  of  the  acid  radicle  present.  So  NaHC03,  in  which 
only  one  of  the  two  acid  hydrogens  of  the  carbonic  acid 
is  replaced  by  sodium  is  called  sodium  bicarbonate  to 
distinguish  it  from  Na2CO3,  sodium  carbonate,  in  which 
both  hydrogens  are  replaced.  Acids  like  phosphoric  acid, 
in  which  there  are  three  replaceable  hydrogens  can  give 
three  series  of  salts  according  as  one,  two,  or  all  three 
hydrogens  have  been  replaced.  These  are  known  as 
primary,  secondary,  and  tertiary  phosphates  respectively, 
or  may  be  named  by  putting  the  prefixes  mono,  di,  or 
tri,  before  the  name  of  the  metal.  So  NaH2PO4  may 
be  called  monosodiuin  phosphate  or  primary  sodium  phos- 
phate, while  Na2HPO4is  disodium  phosphate  or  secondary 
sodium  phosphate.  While  these  rules  of  nomenclature 
may  seem  somewhat  complicated  at  first  sight,  a  little 
practice  in  their  application  will  be  sufficient  to  fix  them 
in  the  memory. 

The  bases  make  up  a  third  large  and  important  class 
of  compounds.  They  all  react  with  litmus,  but  turn  it 
blue  instead  of  red  as  acids  do;  their  solutions  have  a 


INORGANIC  CHEMISTRY  39 

more  or  less  soapy  feeling;  and  they  all  contain  the  hyd- 
roxyl  group)  OH,  combined  with  a  metal.  The  most  com- 
mon bases  are  sodium  hydroxide,  NaOH,  potassium 
hydroxide,  KOH,  ammonium  hydroxide,  NH4OH,  and 
calcium  hydroxide,  Ca(OH)2.  They  may  be  regarded 
as  derived  from  water  by  replacing  one  hydrogen  in  the 
molecule  by  a  metal.  Their  most  important  property 
is  that  of  reacting  with  acids  to  form  a  salt  and  water, 
the  hydrogen  of  the  acid  combining  with  the  hydroxyl 
of  the  base  to  form  water,  while  the  metal  and  the  acid 
radicle  go  together  to  form  a  salt. 

NaOH  +  HC1  =  H2O  +  NaCl. 
Ca(OH)2  +  H2C03  =  2H20  +  CaCO3. 

This  reaction  between  acids  and  bases  is  known  as 
neutralization. 

The  terms  base  and  alkali  are  sometimes  used  inter- 
changeably although  they  are  not  quite  synonymous. 
A  base  is  a  substance  which  answers  in  every  particular 
to  the  description  given  above,  while  an  alkali  may  or 
may  not  contain  hydroxyl  but  on  dissolving  in  water 
gives  a  solution  with  basic  properties.  All  soluble 
hydroxides  are  bases,  and  all  bases  may  be  called  alkalies, 
or  be  said  to  be  alkaline,  but  some  substances  which  are 
not  hydroxides,  such  as  sodium  carbonate,  Na2C03,  are 
also  called  alkalies  because  their  solutions  in  water  show 
the  properties  of  a  base.  This  is  due  to  the  fact  that  they 
tend  to  react  with  the  water  to  some  extent,  producing  a 
basic  solution.  Sodium  and  potassium  hydroxides  which 
are  strong  bases  with  a  caustic  or  corrosive  action  on  the 
skin  are  sometimes  called  caustic  alkalies,  while  sodium 
and  potassium  carbonate  are  known  as  mild  alkalies  as 
their  action  is  much  less  strong.  These  last  are  also 
occasionally  spoken  of  as  fixed  alkalies,  to  distinguish 
them  from  ammonium  carbonate  which  is  volatile. 


40  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

Every  atom  of  acid  hydrogen  will  combine  with  one 
hydroxyl  from  a  base.  Accordingly  acids  with  only  one 
replaceable  hydrogen  are  called  monobasic  since  they  will 
react  with  only  one  basic  OH ;  those  with  two  replaceable 
hydrogens  are  called  dibasic,  and  those  with  three  are 
tribasic.  Similarly,  we  may  speak  of  mono-,  di-,  and  tri- 
acidic  bases,  according  as  they  react  with  one,  two,  or 
three  atoms  of  acid  hydrogen. 


CHAPTER  V 
ELECTROLYTES  AND  IONIZATION 

Electricity  is  a  powerful  force  of  which  we  know  little 
except  its  effects  and  the  fact  that  it  can  be  conveyed 
from  one  point  to  another,  passing  through  certain 
substances  which  are  called  conductors  much  as  water 
passes  through  a  pipe.  Metals  such  as  copper,  iron,  and 
so  on,  are  among  the  best  conductors,  that  is,  they  offer 
very  little  resistance  to  the  passage  of  the  current.  Cer- 
tain other  substances,  such  as  glass  or  rubber,  offer  so 
much  resistance  that  the  current  will  not  flow  through 
them  at  all.  They  are  therefore  called  non-conductors 
or  insulators.  The  human  body  is  a  conductor,  so  if  a 
man  touches  one  of  the  poles  of  an  electric  battery  he 
gets  a  shock,  more  or  less  severe  according  to  the  strength 
of  the  battery;  that  is,  according  to  the  amount  of  elec- 
tricity which  it  produces.  If  his  hand  is  protected  with 
a  thick  rubber  glove,  or,  better,  if  he  handles  the  wires 
with  a  glass  rod,  he  will  feel  no  effect  as  the  current  is 
unable  to  pass  through  the  insulating  material  into  his 
fingers. 

Electricity  appears  to  be  of  two  kinds,  which,  for 
convenience  sake,  are  distinguished  as  positive  and  nega- 
tive, often  represented  by  the  signs  +  and  — .  Any 
body  which  contains  electricity,  or  from  which  an  elec- 
tric current  will  flow,  is  said  to  be  charged  with  electric- 
ity. A  charge  may  be  produced  by  various  means;  as 
a  result  of  chemical  action,  when  the  chemical  energy  of 
the  reacting  substances  is  transformed  into  electrical 
energy,  as  is  seen  in  the  storage  battery  in  common  use, 

41 


42  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

or  by  friction,  when  mechanical  energy  is  converted  into 
electrical  energy.  A  simple  example  of  this  last  may  be 
seen  when  the  hair  is  combed  on  a  very  dry  cold  day. 
The  separate  hairs  stand  out  from  the  head  and  crackle, 
and  sometimes  even  send  out  visible  sparks.  Bodies 
are  said  to  be  positively  or  negatively  charged  according 
as  the  electricity  which  they  contain  is  positive  or  negative, 
but  whenever  a  charge  of  one  kind  is  developed  on  one 
body  an  equal  amount  of  the  opposite  kind  is  developed 
upon  some  other  body  at  the  same  time.  It  is  a  curious 
fact  that  two  bodies  charged  with  positive  electricity  or 
two  bodies  charged  with  negative  electicity  will  tend  to 
repel  each  other,  whereas  bodies  charged  with  opposite 
kinds  of  electricity  have  a  strong  attraction  for  each  other. 
In  the  example  given  above  the  hairs  are  charged  with 
one  kind  of  electricity,  while  an  equal  amount  of  the 
opposite  kind  is  developed  upon  the  comb,  and  accord- 
ingly each  separate  hair  stands  out  as  far  from  its 
neighboring  hairs  as  possible  but  tries  to  cling  to  the 
comb. 

If  an  electric  battery  is  used  as  a  source  of  electricity 
the  two  wires,  or  poles  as  they  are  called,  leading  from 
the  battery  will  be  charged,  one  with  positive  and  the 
other  with  negative  electricity.  If  they  are  connected 
by  some  conducting  material  a  current  will  flow  through 
the  circuit  thus  made,  but  if  a  non-conductor  is  placed 
between  the  two  poles  no  current  passes.  This  can  be 
shown  by  introducing  into  the  circuit  a  measuring  instru- 
ment known  as  a  galvanometer  which  indicates  by  means 
of  a  pointer  moving  over  a  scale  the  force  of  the  current 
passing  between  two  points. 

If  the  poles  of  the  battery  are  dipped  into  pure  water 
no  current  will  pass  between  them,  as  pure  water  is  a 
non-conductor,  and  similarly  if  perfectly  dry  salt  be 
placed  between  the  poles  the  current  is  interrupted. 


INORGANIC  CHEMISTRY  43 

But  if  a  little  salt  is  dissolved  in  the  water  the  galva- 
nometer pointer  will  move,  showing  that  a  current  is  now 
passing.  Substances  which  when  dissolved  in  water 
are  able  to  carry  a  current  of  electricity  are  called 
electrolytes,  and  it  has  been  found  that  acids,  bases,  and 
salts  alone  have  this  power. 

The  passage  of  electricity  through  a  solution  of  an 
electrolyte  might  at  first  be  supposed  to  be  exactly  like 
its  passage  through  a  metallic  conductor  such  as  a 
telephone  wire.  There  is,  however,  one  important 
difference.  The  metal  remains  unchanged  by  the  pas- 
sage of  the  current,  whereas  in  the  case  of  an  electrolyte 
conductance  is  always  accompanied  by  chemical  action, 
the  electrolyte  being  decomposed.  In  order  to  explain 
this,  and  at  the  same  time  to  answer  the  question,  How 
is  the  current  carried?  a  theory  known  as  the  ionic  theory 
has  been  devised  which  has  thrown  light  upon  a  great 
number  of  otherwise  inexplicable  phenomena. 

When  acids,  bases,  and  salts  are  dissolved  in  water 
they  are  believed  to  be  separated  by  the  water  into 
particles  called  ions,  each  of  which  carries  an  electric 
charge.  An  ion  may  be  a  single  atom  or  a  group  of 
atoms,  and  owes  its  peculiar  properties  to  the  charge 
which  it  carries.  Acids  separate  into  positive  hydrogen 
ions,  represented  by  putting  a  +  sign  above  the  symbol 
for  hydrogen,  H+,  and  acid  radicles  with  a  negative 
charge,  represented  by  a  —  sign,  Cl",  NO3~,  and  so  on. 
Bases  give  positive  metal  ions  and  negative  hydroxyl 
ions,  e.g.  NaOH  gives  Na+  and  OH~.  Salts  being 
formed  by  the  combination  of  positive  metals  and  nega- 
tive acid  radicles  separate  into  these  ions  again,  so  NaCl 
dissociates  into  Na+  and  Cl" .  An  ion  which  is  negatively 
charged  will  be  attracted  toward  the  positive  pole  of 
the  battery,  the  positive  electrode  or  anode  as  it  is  called, 
and  will  move  through  the  water  towards  it,  while  a 


44  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

positively  charged  ion  on  the  other  hand  will  travel 
away  from  the  anode  towards  the  negative  electrode  or 
cathode.  Positive  ions  are  therefore  called  cations  and 
negative  ions  are  called  anions  to  indicate  the  direction 
in  which  they  move  through  the  solution.  The  amount 
of  electricity  carried  by  an  ion  is  in  direct  proportion 
to  its  valence.  A  monovalent  atom  or  group  carries 
one  unit  charge,  a  divalent  atom  two  such  charges,  and 
trivalent  atoms  three. 

If  a  positively  and  a  negatively  charged  ion  happen  to 
come  into  sufficiently  close  contact  the  charges  neutralize 
each  other  and  a  molecule  is  formed.  On  the  other 
hand  there  is  always  a  tendency  on  the  part  of  the  water 
to  separate  the  molecules  into  ions  again,  so  that  in  any 
solution  there  is  a  continual  breaking  up  of  molecules 
into  ions  and  recombining  of  ions  into  molecules.  These 
two  actions  go  on  at  precisely  the  same  rate  so  that  the 
sum  total  of  the  ions  and  molecules  present  remains 
always  the  same  unless  their  equilibrium  is  disturbed 
by  the  addition  or  removal  of  water  or  salt.  When  an 
anion  reaches  the  anode  or  a  cation  the  cathode  it  gives 
up  its  charge  and  becomes  an  atom  (or  group)  again, 
another  ion  being  always  discharged  simultaneously  at 
the  opposite  pole.  This  would  tend  to  reduce  the  num- 
ber of  ions  in  the  solution  were  it  not  that  the  balance  is 
immediately  restored  by  the  breaking  up  of  another 
molecule  into  ions  again  .to  replace  those  discharged 
at  the  electrodes. 

Under  ordinary  conditions  the  molecules  of  a  dissolved 
substance  are  never  all  dissociated  into  ions,  the  propor- 
tion between  ionized  and  unionized  molecules  depending 
partly  on  the  nature  of  the  substance  in  solution  and 
partly  on  the  strength  of  the  solution.  As  one  might 
expect,  since  it  is  the  water  that  causes  this  dissociation 
to  tfake  place,  the  more  dilute  the  solution  the  greater 


INORGANIC  CHEMISTRY  45 

the  number  of  molecules  broken  down  into  ions.  On  the 
other  hand,  in  solutions  of  equal  strength  some  substances 
are  highly  ionized  while  others  are  only  very  slightly 
ionized.  All  salts  are  highly  ionized,  as  are  also  the 
three  common  acids,  sulphuric,  hydrochloric  and  nitric, 
and  the  bases  sodium  and  potassium  hydroxides.  All 
other  acids  and  bases  are  much  less  ionized.  Since  it 
is  precisely  those  acids  and  bases  which  are  much  ionized 
that  are  known  to  be  "  strong, "  that  is  to  display  most 
markedly  the  acid  or  basic  characteristics,  while  those 
that  are  little  ionized  are  weak,  and  moreover  since 
neither  acids  nor  bases  if  perfectly  free  from  water  will 
conduct  a  current,  act  on  litmus  paper,  or  show  any  of 
the  properties  which  we  expect  of  them,  we  are  led  to 
believe  that  these  properties  are  entirely  due  to  the  ions 
and  not  to  the  molecules.  That  is,  the  so-called  acid 
properties  are  properties  of  the  hydrogen  ion;  when 
there  are  many  of  these  ions  present  in  the  solution  it 
will  be  strongly  acid;  the  fewer  there  are  the  weaker 
does  the  acid  appear.  Similarly,  the  basic  properties 
of  hydroxides  are  due  to  the  hydroxyl  ion.  Since  all 
acids  give  hydrogen  ions  and  all  bases  give  hydroxyl 
ions  we  would  expect  a  great  similarity  between  the 
different  members  of  these  two  groups,  which  we  find 
to  be  the  case.  Neutralization,  in  the  light  of  the  ionic 
theory,  is  to  be  looked  upon  not  as  a  reaction  between 
a  molecule  of  acid  and  a  molecule  of  base  so  much  as  a 
reaction  between  a  hydrogen  ion  and  an  hydroxyl  ion 
to  form  water;  the  metal  from  the  base  and  the  acid 
radicle  from  the  acid  remain  in  the  solution  for  the  most 
part  as  separate  ions  until  evaporation  of  the  solution 
brings  them  so  close  together  that  they  unite  to  form 
molecules  of  salt. 

In  all  reactions  in  which  salts  are  concerned  it  is  the 
ions  rather  than  the  molecules  of  the  salt  which  take  part. 


46  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

An  ion,  like  an  atom,  always  maintains  its  individual 
characteristics  from  whatever  source  it  comes,  so  the 
S04  ion,  for  example,  will  always  act  in  the  same  way 
whether  it  comes  from  the  dissociation  of  a  molecule 
of  H2S04  or  a  molecule  of  Na2S04.  This  simplifies 
the  study  of  chemistry  considerably,  as  we  can  learn 
certain  reactions  of  sulphates  in  general  or  of  sodium 
salts  in  general  instead  of  learning  the  properties  of 
each  member  of  the  group. 

Electrolytes  play  an  important  part  in  the  life  processes. 
They  are  the  most  effective  agents  in  maintaining  the 
osmotic  pressure  of  the  body  fluids  and  so  regulating  the 
flow  of  substances  into  and  out  of  the  cells.  That  this 
is  not  their  sole  function  however  is  indicated  by  the  fact 
that  solutions  of  equal  strengths  of  different  salts  are 
not  exactly  equivalent  physiologically.  The  various  ions 
have  probably  specific  functions  as  well  as  a  combined 
effect.  A  few  of  these  special  functions  are  recognized 
already,  although  much  remains  to  be  learned  about 
them.  It  has  been  found  for  instance  that  the  normal 
beating  of  the  heart  is  dependent  partly  on  the  calcium 
ions  present  and  partly  on  the  sodium  and  potassium 
ions.  Sodium  salts  are  known  to  exercise  a  pronounced 
influence  on  the  irritability  of  the  muscles.  Calcium 
ions  are  essential  for  the  clotting  of  the  blood  and  are 
sometimes  added  with  beneficial  effect  in  certain  cases 
where,  owing  to  the  abnormal  composition  of  the  blood, 
clotting  will  not  take  place  naturally  and  there  is  in  conse- 
quence excessive  loss  of  blood  from  the  slightest  wound 
or  abrasion  of  the  skin. 

An  important  function  of  vegetables  and  fruits  in  the 
diet  is  to  supply  the  necessary  salts  and  acids  for  the 
body,  and  when  these  are  too  restricted  in  amount  ill 
effects  very  soon  make  themselves  felt.  Sodium  in  the 
form  of  sodium  chloride  is  added  to  the  food  as  seasoning 


INORGANIC  CHEMISTRY  47 

and  is  therefore  always  present  in  sufficient,  if  not  exces- 
sive amounts.  Potassium  salts  are  present  in  meat  and 
in  many  vegetables  and  these  along  with  various  other 
salts  of  which  comparatively  small  quantities  are  re- 
quired are  probably  always  present  in  sufficient  amounts 
in  the  ordinary  mixed  diet  of  the  average  American. 
Calcium  in  the  form  of  calcium  phosphate,  necessary 
not  only  for  maintaining  the  proper  supply  of  calcium 
ions  in  the  tissues  but  also  for  building  up  the  bony 
tissue  of  the  body,  is  obtained  largely  from  milk,  hence 
the  necessity  for  a  plentiful  supply  of  this  food,  particu- 
larly for  growing  children  who  are  forming  bony  tissue. 


CHAPTER  VI 
THE  HALOGENS 

The  elements  chlorine  (Cl),  bromine  (Br),  and  iodine 
(I),  together  with  the  less  common  fluorine  (Fl),  make 
up  what  is  known  as  &  family  of  elements.  The  different 
members  bear  a  very  strong  resemblance  to  one  another, 
the  chemical  and  physical  properties  varying  in  regular 
order  with  increase  or  decrease  in  the  atomic  weight, 
from  fluorine  which  is  the  lightest  up  to  iodine  which  is 
the  heaviest. 

This  family  is  known  collectively  as  the  halogens  (from 
two  Greek  words  meaning  salt  formers),  so  called  because 
they  are  found  in  sea  water  and  it  is  largely  to  compounds 
of  these  elements,  particularly  of  chlorine,  that  sea  water 
owes  its  salty  taste.  They  are  monovalent,  and  com- 
bine with  hydrogen  to  form  acids,  hydrochloric  acid, 
HC1,  hydrobromic  acid,  HBr,  and  hydriodic  acid,  HI; 
and  with  metals  to  form  halides,  sodium  chloride,  NaCl, 
sodium  bromide,  NaBr,  sodium  iodide,  Nal. 

Chlorine  is  a  greenish  yellow  gas  which  can  easily  be 
condensed  into  a  liquid.  It  has  an  intensely  disagreeable, 
suffocating  odor  and  a  very  irritating  action  on  the 
mucous  membrane  of  the  nose  and  mouth.  When 
dissolved  in  water  it  reacts  with  it,  giving  one  molecule 
of  hydrochloric  acid  and  one  molecule  of  hypochlorous 
acid. 

C12  +  H2O  =  HC1  +  HC1O. 

Hypochlorous  acid,  HC1O,  is  an  unstable  compound  and 
decomposes  readily,  especially  in  the  sunlight,  setting 
free  oxygen. 

HC10  =  HC1  +  O. 

48 


INORGANIC  CHEMISTRY  49 

The  oxygen  thus  set  free  is  in  a  particularly  active  state 
and  therefore  chlorine  in  the  presence  of  moisture  is  a 
most  effective  oxidizing  agent.  It  is  largely  used  for 
bleaching,  as  it  oxidizes  vegetable  coloring  matter  to 
colorless  compounds.  It  also  finds  extensive  use  in  the 
purification  of  water,  the  bacterial  and  other  impurities 
being  oxidized  to  harmless  substances. 

Bleaching  powder  is  the  calcium  compound  of  the  mixed 
hydrochloric  and  hypochlorous  acids  formed  when 
chlorine  is  dissolved  in  water.  It  decomposes  like  hy- 
pochlorous acid  itself,  setting  free  oxygen,  and  is  there- 
fore an  oxidizing  agent.  It  is  much  used  for  bleaching, 
disinfecting,  and  deodorizing.  Being  a  solid  it  is  in 
more  convenient  form  for  ordinary  use  than  the  free 
chlorine. 

Bromine  is  a  heavy  dark  red  liquid  which  gives  off 
irritating  fumes  and  has  a  very  corrosive  action  on  the 
skin,  causing  a  serious  burn  if  allowed  to  remain  in 
contact  with  it  even  for  a  moment.  The  free  element 
is  not  used  except  in  the  preparation  of  chemicals. 
Sodium,  potassium,  and  ammonium  bromides  are  all 
used  medicinally  as  sedatives. 

Iodine  is  a  metallic-looking,  dark  grey  solid  which 
gives  off  violet  fumes  on  warming.  It  is  almost  insoluble 
in  water,  but  dissolves  readily  in  alcohol  and  in  an  aque- 
ous solution  of  potassium  iodide.  A  mixture  of  iodine 
and  potassium  iodide  dissolved  in  alcohol  is  known 
as  tincture  of  iodine.  Free  iodine  has  valuable  antiseptic 
properties  and  is  much  used  in  the  dressing  of  wounds, 
etc.  Various  compounds  of  iodine  are  used  in  medicine. 


CHAPTER  VII 
CATALYSTS  AND  ENZYMES. 

Some  chemical  reactions  will  take  place  either  not  at 
all  or  only  very  slowly  except  in  the  presence  of  some 
other  substance  which  is  itself  not  altered  in  the  course 
of  the  reaction.  Such  a  substance  is  called  a  catalyst 
or  catalytic  agent,  from  two  greek  words  meaning  to 
loosen,  since  the  action  of  the  catalyst  seems  to  consist  in 
a  loosening  or  setting  free  of  the  forces  which  bring  about 
the  reaction.  The  most  striking  peculiarity  about  catal- 
ysts is  that  very  small  quantities  are  required,  sometimes 
the  most  minute  trace  of  catalyst  being  sufficient  to 
cause  reaction  between  large  amounts  of  substances, 
and  even  this  small  amount  can  be  recovered  unchanged 
when  the  reaction  has  come  to  an  end. 

The  most  diverse  substances  act  as  catalysts.  Plati- 
num, especially  when  very  finely  divided  or  spongy,  is 
used  in  many  commercial  processes.  Copper  is  a  very 
efficient  catalyst  in  certain  cases.  Many  reactions 
will  take  place  in  the  presence  of  a  trace  of  moisture  which 
would  not  go  on  if  the  reagents  used  were  perfectly  dry; 
for  instance  hydrogen  and  oxygen  which  combine  with 
explosive  violence  when  heated  to  about  1100°  F.  can 
be  heated  to  almost  twice  this  temperature  without  ex- 
plosion if  care  has  been  taken  to  have  both  gases  abso- 
lutely dry. 

The  ease  and  rapidity  with  which  the  most  complicated 
and  difficult  reactions  can  be  carried  on  in  the  living  cell 
without  the  aid  of  high  temperature  or  strong  reagents 
could  only  be  explained  after  the  discovery  that  innumer- 

50 


INORGANIC  CHEMISTRY  51 

able  catalysts  exist  in  plant  and  animal  organisms. 
Some  of  these  catalysts  can  be  separated  from  the  cells 
and  will  exert  their  characteristic  influence  on  reactions 
outside  of  the  organism ;  others  have  never  been  isolated, 
but  their  presence  is  recognized  by  the  reactions  which 
they  bring  about.  These  catalysts  which  are  produced 
by  the  living  organism  and  by  means  of  which  it  carries 
on  its  vital  processes  are  called  enzymes  or  ferments. 
As  is  the  case  with  all  catalysts,  a  very  small  amount  of 
enzyme  will  bring  about  a  large  amount  of  reaction. 
Each  enzyme  influences  one  special  reaction  and,  so  far 
as  we  know,  only  one.  Even  very  closely  related  sub- 
stances like  the  different  sugars  have  each  a  special 
enzyme  which  acts  upon  it  causing  one  specific  kind  of 
reaction.  So  in  the  digestive  juices  there  is  an  enzyme 
to  act  on  cane  sugar,  an  enzyme  to  act  on  milk  sugar, 
and  an  enzyme  to  act  on  malt  sugar,  decomposing  these 
to  simpler  sugars  which  may  then  be  acted  on  by  still 
other  enzymes  causing  further  decomposition  or  building 
these  up  into  new  complexes,  according  to  the  needs  of 
the  body. 

Enzymes  are  very  sensitive  to  conditions.  They  can 
stand  a  cestain  rather  limited  range  of  temperature,  but 
there  is  for  each  enzyme  a  minimum  temperature  below 
which  it  cannot  act,  a  maximum  temperature  above 
which  it  cannot  act,  and  an  optimum  temperature  at 
which  its  effect  is  most  marked.  Moreover  they  are 
very  sensitive  to  small  amounts  of  strong  acids  or  alkali. 
Some  enzymes  will  act  only  in  faintly  alkaline  solution, 
some  only  in  somewhat  acid  solution,  and  some  prefer  a 
neutral  medium.  In  every  case  even  a  slight  excess  of 
either  acid  or  alkali  will  destroy  the  enzyme. 

Enzymes  are  frequently  produced  in  the  cell  in  a  pe- 
culiar form  known  as  zymogens.  Zymogens  are  much 
more  resistive  to  unfavorable  influence  of  heat,  acid,  or 


52  CHEMISTBY  FOR  NURSES  AND  STUDENTS 

alkali  than  are  the  enzymes.  They  are  inactive,  but  can 
be  converted  into  the  active  form  (activated)  by  other 
substances  which  the  cell  produces  when  necessary. 
The  enzymes  are  classified  and  named  according  to  the 
substances  on  which  they  act,  with  the  exception  of  a 
few  which  were  known  and  named  before  this  system  of 
nomenclature  was  devised.  So  the  enzymes  which 
decompose  proteins  are  called  proteases  or  proteolytic 
enzymes,  but  the  two  most  important  members  of  this 
class  which  are  found  in  the  stomach  and  intestines  are 
known  as  pepsin  and  trypsin  respectively.  The  enzymes 
which  act  on  fats  are  called  Upases  or  lipolytic  enzymes 
(from  lipin,  a  term  used  to  include  all  fat-like  sub- 
stances). The  starch  hydrolyzing  enzymes  are  called 
amylases  (from  the  Latin  amylum,  starch),  or  diastases 
or  diastatic  enzymes  from  their  relation  to  the  original 
diastase,  the  starch  hydrolyzing  enzyme  of  the  barley 
grain. 


CHAPTER  VIII 

NITROGEN  AND  THE  ATMOSPHERE 

If  a  lighted  candle  is  put  in  an  enclosed  space  it  burns 
for  a  time,  the  flame  becoming  dimmer  and  more  smoky, 
until  it  finally  goes  out.  If  a  fresh  candle  or  a  burning 
match  be  inserted  in  this  same  space  it  will  be  immedi- 
ately extinguished.  Knowing  that  combustion  is  a 
process  of  oxidation  we  can  explain  this  as  due  to  the 
using  up  of  the  oxygen  of  the  air  by  the  burning  candle, 
combustion  being  less  and  less  complete  as  the  oxygen 
becomes  more  and  more  exhausted,  until  finally  there  is 
no  more  oxygen  and  there  can  be  no  more  burning. 
What  is  left  when  all  the  oxygen  of  the  air  is  used  up? 
Experiment  shows  that  the  residue  is  a  mixture  of  the  gas 
nitrogen  (N)  with  traces  of  other  gases  such  as  carbon 
dioxide,  water  vapor,  etc.  This  mixture  resembles  air 
in  its  appearance  and  superficial  character  but  an  animal 
placed  in  it  dies  of  suffocation.  If  more  oxygen  is  added 
to  it  the  gas  takes  on  once  more  the  character  of  atmos- 
pheric air,  without  evidence  of  any  chemical  reaction 
taking  place.  From  this  and  from  the  fact  that  the 
proportions  of  the  different  gases  vary  from  time  to  time 
without  altering  the  character  of  the  air  we  conclude  that 
the  atmosphere  is  a  mixture  of  gases,  chiefly  oxygen  and 
nitrogen  in  the  proportion  of  one  part  of  oxygen  to  four 
of  nitrogen,  not  a  compound  formed  by  the  combination 
of  these  gases. 

Animal  life  necessitates  taking  in  oxygen  through  the 
lungs,  using  it  to  oxidize  the  complex  substances  of  the 
tissues,  and  breathing  it  out  again  as  carbon  dioxide,  the 

53 


54  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

result  being  that  the  oxygen  of  the  atmosphere  is  de- 
creased and  the  carbon  dioxide  increased  by  living 
animals.  The  following  table  shows  the  average  rela- 
tive composition  of  air  as  breathed  into  and  breathed 
out  from  the  lungs. 

Inspired  Expired 

Oxygen 20.94  16.4 

Carbon  dioxide 0.03  4.1 

Nitrogen 78.09  78.09 

Plants,  on  the  other  hand,  while  using  a  certain  amount 
of  oxygen  for  this  same  purpose,  are  at  the  same  time 
taking  in  carbon  dioxide  to  form  complex  molecules 
which  are  reduction  products  and  therefore  contain 
less  oxygen  than  the  carbon  dioxide  used  in  their  forma- 
tion. This  excess  of  oxygen  is  given  up  by  the  plant 
to  the  atmosphere,  so  that  plant  life  results  in  diminish- 
ing the  carbon  dioxide  and  increasing  the  oxygen  of  the 
atmosphere. 

In  considering  the  cause  of  the  ill-effects  produced  by 
"bad  air, "  that  is  the  air  of  an  ill-ventilated  room,  the 
relative  proportion  of  carbon  dioxide  and  oxygen  present 
was  formerly  regarded  as  of  prime  importance.  This 
was  a  natural  supposition,  since  the  importance  of  oxygen 
for  life  has  long  been  known,  as  has  also  the  fact  that 
carbon  dioxide  will  not  support  life.  Of  late  years, 
however,  it  has  been  demonstrated  beyond  possibility 
of  doubt  that  the  variation  in  these  factors  due  to  even 
the  worst  conditions  of  overcrowding  and  lack  of  ventila- 
tion is  much  too  small  to  be  of  any  practical  importance. 
Experience  has  shown  that  the  oxygen  of  the  air  can  be 
reduced  to  less  than  17  per  cent.,  that  is  to  a  proportion 
which  will  no  longer  support  combustion,  before  any 
ill  effects  can  be  observed.  It  would  seem  therefore 
that  any  air  in  which  a  match  will  burn  contains  sufficient 
oxygen  for  a  human  being  to  breathe.  Similarly,  it 


INORGANIC  CHEMISTRY  55 

has  been  shown  that  carbon  dioxide  does  not  become 
harmful  until  it  reaches  1  per  cent.,  while  in  one  experi- 
ment a  man  spent  twenty-four  hours  in  an  atmosphere 
containing  over  2  per  cent,  and  was  observed  to  be  in 
unusually  good  spirits  during  this  time.  In  crowded 
rooms  the  carbon  dioxide  rarely  reaches  0.25  per  cent., 
so  it  would  seem  that  this  factor  also  may  be  disregarded. 

Another  theory  supposed  that  some  organic  substance 
was  present  in  expired  air,  in  traces  too  minute  to  be 
detected  by  ordinary  means,  but  very  toxic  even  in  such 
small  amount.  This  view  was  supported  to  some  extent 
by  the  very  unpleasant  odor  of  a  room  crowded  with 
human  beings.  Absolutely  no  proof  has  been  found, 
however,  of  any  such  toxic  substance.  On  the  con- 
trary, there  is  evidence  to  show  that  even  the  most 
vitiated  air  can  be  breathed  into  the  lungs  without  injury. 
A  number  of  people  were  confined  in  a  small  air-tight 
room  until  they  began  to  grow  faint  and  ill,  while  another 
man,  stationed  outside  the  room  but  breathing  the  same 
air  through  a  tube  felt  perfectly  comfortable.  On  the 
other  hand  no  relief  was  felt  by  the  sufferers  when  they 
were  allowed  to  breathe  the  outside  air  through  a  tube. 
Then  an  electric  fan  was  started  in  the  room  without 
changing  the  air  in  any  other  way  than  by  setting  it  in 
motion.  Those  inside  immediately  revived  and  felt  as 
though  fresh  air  had  been  admitted.  From  this  and 
many  other  similar  experiements  hygienists  have  come 
to  the  conclusion  that  it  is  not  the  chemical  composition 
of  the  air  which  is  important  but  the  temperature  and 
amount  of  moisture  present. 

The  human  body  is  continually  producing  heat,  most 
of  which  passes  out  from  the  body  through  the  skin, 
either  by  radiation  into  the  atmosphere  or  by  evaporation 
of  the  moisture  on  the  surface  of  the  skin.  If  its  escape 
is  prevented  the  temperature  of  the  body  rises,  the  nor- 


56  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

mal  action  of  the  cells  is  disturbed,  lassitude  and  fatigue 
are  felt,  followed  by  all  the  symptoms  of  heat  prostration. 
Accumulation  of  heat  in  the  body  is  always  unfavorable 
and  may  be  caused  either  by  high  temperature  of  the 
surrounding  air  which  prevents  radiation  of  heat  from  the 
body,  or  by  high  humidity  (moisture  content)  which 
prevents  rapid  evaporation  of  moisture  from  the  skin. 
It  is  well  known  that  a  warm  humid  day  in  summer  causes 
more  heat  prostrations  than  a  much  hotter  day  when  the 
air  is  drier.  The  ill-effects  of  humidity  in  our  rooms  in 
winter  are  not  so  obvious,  but  make  themselves  felt  none 
the  less.  Unfortunately  the  ideal  humidity  at  different 
temperatures  has  not  yet  been  ascertained.  Too  little 
moisture  makes  an  uncomfortable  atmosphere  just  as 
does  too  much,  and  this  is  perhaps  a  more  common 
defect  in  our  artificially  heated  houses.  Over-heating 
is  equally  or  perhaps  more  common  amongst  us.  A  body 
will  radiate  heat  only  when  it  is  in  contact  with  some- 
thing cooler  than  itself,  and  the  greater  the  difference  in 
temperature  the  more  rapidly  does  radiation  take  place. 
The  higher  the  temperature  of  the  air  therefore  the  less 
heat  is  lost  by  radiation  from  the  body.  If  the  air  is 
dry  this  may  be  partially  compensated  by  the  increased 
evaporation,  but  if  the  air  is  both  moist  and  hot  both 
methods  of  escape  are  prevented  and  the  heat  rapidly 
accumulates  to  a  dangerous  degree.  Hygienists  agree 
that  except  for  old  people,  who  need  a  slightly  higher 
temperature,  a  room  should  not  be  kept  above  70°. 
There  is  a  little  more  difference  of  opinion  about  the 
desirable  lower  limit.  In  this  country  it  is  usually  put 
about  65°,  but  the  English  authorities  consider  60°, 
or  even  below  that,  more  healthful.  Probably  custom 
has  a  good  deal  to  do  with  it,  as  the  body  is  known  to 
have  considerable  power  of  adaptation  and  can  gradually 
be  accustomed  to  a  temperature  many  degrees  lower  than 


INORGANIC  CHEMISTRY  57 

that  previously  found  comfortable.  It  must  be  remem- 
bered here,  however,  as  in  all  cases  where  a  change  in 
the  living  conditions  of  a  human  being  is  concerned, 
that  the  change  must  not  be  made  too  suddenly.  Suffi- 
cient time  must  always  be  allowed  for  readjustment  to 
take  place  if  discomfort  is  to  be  avoided. 

Occasional  changes  of  temperature,  within  reason, 
seem  better  than  a  steady  level,  as  the  change  has  a 
stimulating  effect.  Also,  air  that  is  in  motion  is  better 
than  air  which  is  perfectly  still  as  the  currents  convey 
the  hot  moist  air  away  from  the  body  and  thus  assist 
both  radiation  and  evaporation.  The  ill  effects  of  drafts 
on  the  other  hand  seem  to  be  due  to  the  chilling  down 
of  the  body  at  one  point  too  suddenly  to  allow  of  its 
protecting  itself  by  producing  more  heat  as  it  does  when 
the  reduction  is  more  gradual  or  more  general.  Just 
when  moving  air  ceases  to  be  beneficial  and  becomes 
an  injurious  draft  is  a  little  difficult  to  determine.  A 
good  deal  depends  on  the  individual,  as  some  people 
are  more  sensitive  to  changes  of  temperature  than  are 
others.  Also  the  state  of  health  of  the  individual  is 
important,  as  a  robust  person  can  withstand  a  shock 
under  which  a  weaker  person  would  collapse. 

Although  we  have  entirely  given  up  the  idea  that  it  is 
necessary  to  keep  our  windows  open  in  order  to  secure 
an  adequate  supply  of  oxygen  for  our  lungs  we  are  still 
largely  dependent  on  window  ventilation  to  cool  and 
humidify  our  air  and  keep  it  in  motion.  Especially 
at  night,  or  in  a  sick-room  where  the  patient  is  warmly 
covered  up  in  bed  and  protected  from  chill,  it  is  possible 
to  regulate  the  temperature  very  satisfactorily  by  this 
means.  Doubtless  in  the  course  of  time  our  engineers 
and  architects  will  co-operate  to  produce  buildings  in 
which  the  ideal  conditions  will  be  secured  automatically, 
but  meantime  probably  the  best  advice  we  can  give 


58  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

the  public  in  general,  especially  our  heat-loving  American 
public,  is  Keep  your  windows  open.  It  must  be  re- 
membered, however,  that  the  purpose  of  the  open 
window  is  chiefly  to  prevent  over-heating,  and  that  this 
may  be  brought  about  also  by  economy  of  fuel,  a  point 
which  is  of  some  importance  to  families  of  limited  income 
or  in  time  of  a  coal  famine.  It  is  perhaps  fortunate  for 
the  public  health  that  the  majority  of  modern  houses 
have  such  loose-fitting  doors  and  windows  as  to  secure 
ventilation  with  or  without  the  will  of  the  occupants. 


CHAPTER  IX 
COMPOUNDS  OF  NITROGEN 

Free,  that  is,  uncombined  nitrogen  is  comparatively 
uninteresting,  but  its  compounds  are  of  fundamental  im- 
portance. Organic  nitrogen  derivatives  known  as  pro- 
teins (see  page  104)  are  used  in  building  up  the  muscular 
tissue  of  animals,  and  it  is  therefore  necessary  that  a 
certain  amount  of  this  element  in  a  suitable  form  be  sup- 
plied regularly  in  the  food.  Animals  have  no  power  of 
making  use  of  free  nitrogen  and  the  enormous  supply 
of  nitrogen  in  the  atmosphere  is  therefore  unavailable 
for  them.  Neither  can  they  use  the  inorganic  salts 
containing  nitrogen,  such  as  the  nitrates  and  nitrites 
(see  page  37)  present  in  the  soil.  They  are  therefore 
dependent  on  the  organic  nitrogen  compounds  which 
they  can  obtain  from  the  plants,  either  directly  or,  in 
the  case  of  flesh  eating  animals,  after  previous  consump- 
tion and  assimilation  by  some  other  animal.  The  plants 
obtain  their  nitrogen  from  nitrates  of  the  soil  which  are 
soluble  and  can  therefore  be  drawn  up  through  the  roots 
in  solution  and  are  then  combined  with  carbon  and  hydro- 
gen to  form  plant  protein.  The  growth  of  plants  results 
therefore  in  the  gradual  removal  of  nitrates  from  the 
soil,  and  these  must  be  restored  to  it  if  it  is  to  remain 
a  good  medium  for  plant  life.  This  is  sometimes  ac- 
complished by  the  use  of  artificial  fertilizers  containing 
nitrates,  or  by  natural  fertilizers  such  as  animal  excreta 
or  dead  animal  or  vegetable  matter  which  in  decaying 
give  up  their  nitrogen  and  return  at  least  part  of  it  to 
the  soil  again  in  soluble  form.  Although  green  plants, 
like  animals,  are  unable  to  use  the  nitrogen  supply  of 

59 


60 


CHEMISTRY  FOR  NURSES  AND  STUDENTS 


the  air  certain  forms  of  bacteria  have  the  power  of  con- 
verting this  free  nitrogen  directly  into  the  useful  ni- 
trates. These  bacteria  grow  in  little  clusters  on  the  roots 
of  leguminous  plants,  peas,  beans,  clover,  etc.  supplying 
more  nitrates  than  the  plant  is  able  to  use  in  its  life- 
time, so  that  the  growth  of  such  plants  results  in  the 
enriching  of  the  soil  instead  of  exhausting  it  as  do  other 
plants.  In  recent  years  successful  commercial  methods 
have  been  devised  for  the  fixation  of  nitrogen,  as  it  is 
called,  that  is,  the  conversion  of  the  atmospheric  nitro- 
gen into  compounds  which  can  be  used  as  plant  food. 
These  are  of  the  utmost  practical  importance  as  they 
insure  an  inexhaustible  supply  of  the  fertilizers  which 
are  directly  essential  for  vegetation  and  indirectly  for 
the  maintenance  of  animal  life  on  the  earth. 

The  cycle  through   which  nitrogen  passes  in  nature 
may  be  represented  by  the  following  diagram: 

Free  fiitroqen 

and 

Nitrogen  Compounds 
the  Atmosphere 


Plant  Waste  \ 
lima  I  Waste\ 


'^^  Living 
Animals 


There  are  two  general  types  of  inorganic  nitrogen 
compounds;  ammonia,  NH3;  and  its  derivatives,  and  the 
acids  containing  nitrogen  and  their  derivatives. 


INORGANIC  CHEMISTRY  61 

Ammonia  is  a  pungent  smelling  gas  which  is  soluble 
in  water,  combining  with  it  to  form  a  base,  ammonium 
hydroxide. 

NH3  +  H2O  =  NH4OH 

On  warming,  the  ammonium  hydroxide  breaks  up  read- 
ily into  NH3  and  H20  again.  The  household  ammonia 
used  in  cleaning  is  a  dilute  solution  of  ammonium  hy- 
droxide. Both  ammonia  gas  and  ammonium  hydroxide 
react  with  acids  to  form  ammonium  salts. 

NH3  +  HC1  =  NH4C1 
NH4OH  +  HC1  =  NH4C1  +  H20 

Many  of  these  salts  have  the  same  tendency  towards 
decomposition  as  ammonium  hydroxide  and  hence  have 
a  strong  odor  of  ammonia  gas. 

NH4C1  =  NH3  +  HC1 

Smelling  salts  are  made  by  mixing  such  a  salt  of  ammonia 
with  some  pleasant-smelling  flower  extract  like  oil  of 
lavendar  and  keeping  the  mixture  tightly  corked. 
The  odor  given  off  when  the  stopper  is  removed  has  a 
refreshing  and  stimulating  effect. 

Ammonia  gas  is  quite  easily  condensed  to  a  liquid  by 
applying  pressure.  When  the  pressure  is  removed  the 
liquid  returns  to  the  gaseous  state  again.  The  differ- 
ence between  a  substance  as  liquid  and  the  same  sub- 
stance in  the  gaseous  state  consists  in  the  different  amount 
of  space  between  the  molecules,  the  molecules  of  a  liquid 
being  held  close  together  while  the  molecules  of  a  gas  are 
so  far  separate  that  each  individual  molecule  has  very  little 
influence  on  its  neighbors.  To  separate  the  particles  of 
a  liquid  requires  work,  or  expenditure  of  energy.  In  our 
common  experience  this  energy  is  supplied  in  the  form 
of  heat,  as  when  we  boil  water  to  convert  it  into  steam. 


62  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

Boiling  water  never  becomes  hotter  than  180°F.,  no 
matter  how  much  fire  we  put  under  it,  because  the  heat 
is  used  up  in  separating  the  molecules  from  one  another 
and  so  converting  the  liquid  water  into  the  gaseous  steam. 
The  more  heat,  the  faster  this  separation  goes  on,  but 
the  temperature  will  not  rise  so  long  as  there  is  any 
liquid  water  left.  When  any  liquid  evaporates,  that  is 
passes  from  liquid  to  vapor,  heat  must  be  used  up,  and 
it  takes  this  heat  from  the  surrounding  air  and  conse- 
quently cools  it  down,  but  if  the  evaporation  is  slow  this 
loss  of  heat  is  so  gradual  as  to  be  unnoticeable.  The 
more  volatile  the  liquid,  that  is,  the  more  rapidly  it 
tends  to  pass  into  vapor,  the  more  pronounced  is  the 
change  in  temperature.  Evaporation  of  moisture  from 
the  skin  gradually  absorbs  heat  from  the  blood  and  re- 
duces the  body  temperature,  hence  the  benefit  of  per- 
spiration in  preventing  dangerous  overheating  of  the 
system.  If  a  drop  of  ether  is  placed  on  the  skin  it  evapo- 
rates a  great  deal  more  rapidly  than  water,  taking  so 
much  heat  from  the  skin  as  it  does  so  that  a  sensation  of 
intense  cold  is  produced.  When  liquid  ammonia  evapo- 
rates it  does  so  very  quickly,  absorbing  much  heat  and 
consequently  lowering  the  temperature  of  its  surround- 
ings to  a  considerable  degree.  If  pipes  through  which 
liquid  ammonia  is  circulating  are  surrounded  with  water 
so  much  heat  will  be  taken  from  the  water  that  it  freezes 
into  solid  ice.  It  is  upon  this  principle  that  the  use  of 
ammonia  in  refrigerating  plants  and  in  making  artificial 
ice  depends.  Ammonia  gas  is  compressed  into  liquid 
and  circulated  through  a  system  of  pipes  where  it  ab- 
sorbs heat  and  evaporates,  only  to  be  compressed  once 
more  and  enter  into  circulation  again,  making  a  continu- 
ous process. 

Nitric  acid,  HNOs,  is  the  most  important  acid  con- 
taining nitrogen.     Besides  being  a  strong  acid  it  is  an 


INORGANIC  CHEMISTRY  63 

excellent  oxidizing  agent,  owing  to  its  tendency  to  break 
up  and  set  free  oxygen. 

2HNO3  =  H2O  +  2NO2  +  O 

This  property  is  shared  by  many  derivatives  of  nitric 
acid,  especially  its  organic  compounds.  Our  most 
powerful  explosives  belong  in  this  class,  and  owe  their 
destructive  power  to  the  fact  that  they  decompose 
with  great  readiness  giving  gaseous  products  which 
expand  into  infinitely  greater  volume  than  the  substance 
from  which  they  were  formed,  and  in  this  sudden  expan- 
sion clear  everything  from  before  them. 


CHAPTER  X 
THE  METALS 

Those  elements  which  can  take  the  place  of  hydrogen 
in  an  acid,  forming  salts,  are  called  metals.  The  metals 
in  general  are  solids,  although  one,  mercury,  is  a  liquid. 
They  are  good  conductors  of  heat  and  of  electricity, 
and  have  a  bright  lustre  which  is  known  as  a  " metallic" 
lustre.  Although  there  is  a  large  number  of  metallic 
elements  only  a  few  are  in  common  use.  These  are 
platinum,  gold,  silver,  iron,  copper,  aluminum,  tin, 
nickle,  lead,  and  zinc. 

Platinum,  Pt,  and  gold,  Au,  are  sometimes  called  the 
"noble"  metals,  because  they  are  not  acted  upon  by 
ordinary  reagents.  The  common  acids  will  not  dis- 
solve them,  nor  do  they  tarnish  in  the  air  as  do  most  other 
metals.  Platinum  is  an  excellent  conductor  of  electricity 
and  has  a  high  melting  point.  Like  iron,  it  softens 
before  melting,  which  makes  it  possible  to  weld  it. 
It  can  be  hammered  into  sheets  or  drawn  out  into  wires, 
and,  as  it  expands  and  contracts  with  change  of  tempera- 
ture at  about  the  same  rate  that  glass  does,  it  can  be 
fused  into  glass.  These  properties,  along  with  its  re- 
sistance to  chemical  agents,  make  it  very  valuable  for 
the  construction  of  scientific  instruments.  It  is  com- 
paratively soft,  however,  and  can  be  rather  easily  bent 
or  scratched. 

Silver,  Ag,  resembles  platinum  in  appearance  and 
certain  physical  properties,  but  is  much  more  easily 
acted  on  by  reagents.  It  dissolves  readily  in  nitric  acid, 
forming  silver  nitrate,  the  substance  sometimes  known  as 

64 


INORGANIC  CHEMISTRY  65 

"lunar  caustic"  and  used  in  medicine  as  a  disinfectant 
and  for  cauterizing.  The  oxygen  of  the  air  has  no  effect 
on  silver,  but  if  the  atmosphere  is  contaminated  by  traces 
of  sulphur  compounds,  as  is  apt  to  be  the  case  where  soft 
coal  or  illuminating  gas  is  used,  the  silver  turns  black, 
owing  to  the  formation  of  a  film  of  silver  sulphide.  This 
is  what  is  known  as  the  tarnishing  of  silver.  The  black- 
ening of  silver  spoons  when  used  for  eggs  is  due  to  the 
sulphur  in  the  egg.  Wool  contains  sulphur,  as  does 
also  vulcanized  rubber,  and  therefore  silver  tarnishes 
quickly  if  left  in  contact  with  either  of  these. 

The  polishing  of  silver  consists  in  removing  this  surface 
of  sulphide.  This  can  be  done  by  rubbing  with  some  sub- 
stance which  is  harder  than  the  silver  but  so  finely 
powdered  that  it  will  not  scratch  the  metal.  Rouge 
(ferric  oxide),  whiting  (powdered  chalk),  and  infusorial 
earth  (made  up  of  the  shells  of  microscopic  animals) 
are  some  of  the  best  substances  for  this  purpose.  Sand 
is  sometimes  found  in  polishing  powders,  but  is  not  a 
desirable  ingredient,  owing  to  the  difficulty  of  reducing  it 
to  a  sufficiently  fine  powder.  These  various  powders 
are  sometimes  made  up  into  a  paste  for  convenience  in 
handling,  but  they  have  little,  if  any,  advantage  over  the 
powders.  In  either  case  vigorous  rubbing  is  necessary 
to  produce  a  polish.  Other  silver  polishes  contain  some 
chemical  which  will  dissolve  silver  sulphide.  With 
these  it  is  not  necessary  to  rub  hard  in  order  to  remove 
the  tarnish,  but  silver  thus  cleaned  has  a  dull  appear- 
ance unless  burnished  by  rubbing  it  briskly  with  chamois 
leather  or  a  soft  cloth  after  the  polish  has  been  removed. 
The  silver  polishing  pans  on  the  market  are  pans  of 
aluminum  or  zinc  in  which  the  silver  is  boiled  with  a 
solution  of  washing  soda  and  salt.  By  a  series  of  reac- 
tions which  are  electro-chemical  in  their  nature,  the 
silver  sulphide  is  decomposed  and  the  sulphur  removed. 


I 

66  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

Here  again  the  silver  is  left  clean  but  not  bright  and 
requires  burnishing. 

Certain  silver  plating  preparations  are  on  the  market, 
to  be  used  instead  of  a  polish.  These  contain  a  small 
amount  of  silver  in  the  form  of  a  compound  from  which 
it  is  deposited  in  a  thin  film  when  it  comes  in  contact 
with  the  article  to  be  polished.  This  is  an  advantage  in 
the  case  of  thinly  plated  silver,  which  tends  to  wear  off 
in  the  course  of  time. 

Pure  silver  is  too  soft  for  ordinary  use,  and  is  hardened 
by  addition  of  a  certain  amount  of  copper.  "  Sterling  " 
silver  contains  92.5  per  cent,  silver  and  7.5  per  cent, 
copper.  On  account  of  the  copper  present  silver  uten- 
sils should  never  be  left  in  contact  with  vinegar  or  with 
foods  containing  vinegar,  as  the  acetic  acid  of  the  vine- 
gar will  react  with  the  copper  forming  a  poisonous  copper 
salt. 

Iron,  Fe,  is  the  most  widely  used  of  all  metals.  Three 
varieties  of  iron  are  known  in  the  industries;  cast  iron, 
steel,  and  wrought  iron.  Wrought  iron  is  almost  pure 
iron,  but  cast  iron  and  steel  contain  varying  small  amounts 
of  other  substances,  of  which  the  most  important  is 
carbon.  It  is  to  the  proportions  of  carbon  present  that 
these  two  varieties  owe  their  specific  properties.  Cast 
iron  is  rather  brittle,  whereas  steel  is  tougher  and  can  be 
tempered  to  almost  any  desired  degree  of  hardness  and 
elasticity.  Overheating  or  too  sudden  cooling  from  a 
high  temperature  will  change  the  temper  of  steel,  and 
for  this  reason  steel  implements  should  never  be  subjected 
to  such  treatment. 

The  rusting  of  iron  is  a  process  of  oxidation  which  takes 
place  only  in  the  presence  of  moist  air.  In  perfectly 
dry  ah-  no  rust  appears,  nor  will  iron  rust  under  water 
free  from  dissolved  air.  All  iron  or  steel  utensils  should 
therefore  be  very  carefully  dried  and  kept  from  damp 


INORGANIC  CHEMISTRY  67 

ness.  Moreover,  any  trace  of  rust  should  be  immediately 
cleaned  off,  as  its  presence  causes  the  rusting  process  to 
go  on  more  rapidly. 

Various  materials  are  used  to  coat  iron  and  protect  it 
from  the  air.  Tin  is  generally  used  for  this  purpose  in 
making  kitchen  utensils  since  tin  it  self  is  not  affected 
by  air  or  moisture.  If  the  tin  layer  is  scratched,  how- 
ever, a  little  electric  current  is  set  up  between  the  tin  and 
the  iron  underneath,  and  the  iron  rusts  faster  than  it 
would  if  there  were  no  tin  there. 

If  iron  is  treated  with  superheated  steam  at  a  high 
temperature  it  forms  another  oxide  with  slightly  different 
proportions  of  iron  and  oxygen  from  those  in  ordinary 
iron  rust.  This  oxide,  instead  of  scaling  off  and  leaving 
fresh  surface  exposed  to  the  action  of  the  air  as  rust 
does,  adheres  firmly  to  the  surface  of  the  iron  and  pro- 
tects it  from  any  further  action.  Roasting  pans  and 
bread  pans  are  made  of  iron  so  treated,  and  are  therefore 
quite  resistive  to  rust,  provided  they  are  kept  dry  when 
not  in  use. 

Iron  covered  with  zinc  is  called  galvanized  iron.  Zinc 
is  a  more  effective  covering  than  tin,  because  even 
though  the  coating  should  become  scratched  or  worn 
through  the  presence  of  zinc  hinders  the  oxidation  of  the 
iron  instead  of  promoting  it  as  does  tin.  Galvanized 
iron  cannot  be  used  for  cooking  utensils,  as  zinc  forms 
poisonous  salts  with  vegetable  acids,  but  it  is  very 
satisfactory  for  water  pipes,  pails,  and  so  on. 

The  enamelled  ware  so  much  used  is  iron  covered  with  a 
glaze  similar  to  that  used  for  china.  It  is  quite  imper- 
vious to  weak  alkalies  and  to  the  dilute  acids  of  fruits  and 
vegetables,  and  if  properly  put  on  the  glaze  will  not  chip 
off  with  ordinary  handling.  Dry  enamel  ware  should 
not  be  subjected  to  sudden  heating  or  cooling  however, 


68  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

as  even  the  best  glaze  is  liable  to  crack  under  those 
conditions. 

Iron  for  water  taps  and  fixtures  of  various  kinds  is 
sometimes  coated  with  nickel.  Nickel  has  very  little 
tendency  to  tarnish  and  is  easily  kept  bright  with  soap 
and  water,  with  occasional  rubbing  with  kerosene  oil 
or  scouring  to  remove  the  film  of  grease  and  dirt  which 
accumulates. 

Copper,  Cu,  is  said  to  be,  next  to  iron,  the  most  useful 
metal.  Enormous  quantities  are  used  for  wiring  in 
electrical  industries,  for  roofing,  for  nails,  rivets  and 
sheathing  in  ship  building,  and  so  on.  In  the  presence 
of  moist  air  copper  tarnishes  rapidly,  becoming  coated 
either  with  brown  oxide  or  with  a  green  carbonate 
known  as  verdigris,  formed  from  the  carbon  dioxide  in 
the  air.  Copper  itself  is  not  acted  on  by  organic  acids,  so 
bright  copper  utensils  can  be  used  in  cooking  with  safety. 
If  they  are  allowed  to  become  tarnished,  however,  the 
organic  acids  will  act  on  the  oxide  or  carbonate  as  the 
case  may  be,  forming  poisonous  salts.  It  is  most 
essential  therefore  that  all  such  utensils  should  be  kept 
in  a  condition  of  high  polish.  Even  polished  copper 
vessels  are  apt  to  contaminate  the  food  with  small 
traces  of  copper,  since  almost  all  fats,  oils,  and  syrups 
dissolve  copper  to  some  extent,  but  the  amount  is  so 
small  that  it  is  not  believed  to  be  injurious  to  health. 

Green  vegetables  cooked  in  copper  boilers  retain  their 
green  color  much  better  than  those  cooked  in  vessels  of 
iron,  tin,  or  enamel.  This  is  sometimes  made  use  of  by 
canners  to  make  their  products  look  attractive,  and  it 
used  to  be  not  uncommon  to  find  canned  peas  to  which 
so  much  copper  had  been  added  that  they  left  a  distinctly 
metallic  taste  in  the  mouth.  Such  highly  contaminated 
vegetables  are  undoubtedly  injurious,  but  fortunately 
the  public  has  been  taught  to  look  with  suspicion  on 


INORGANIC  CHEMISTRY  69 

too  highly  colored  foods,  and  this  bad  practice  is  no 
longer  very  common. 

Ammonia  acts  on  copper  in  the  presence  of  air,  forming 
a  deep  blue  solution.  Ammonia  is  sometimes  used 
in  polishes  for  copper  and  brass.  When  such  a  polish 
is  used  all  traces  of  it  should  be  carefully  removed,  as  its 
presence  would  promote  further  oxidation  of  the  metaL 
The  same  thing  is  true  of  polishes  containing  weak  acids. 

Aluminium,  Al,  oxidizes  superficially  in  moist  air, 
but  the  oxide,  which  is  white,  adheres  firmly  to  the 
surface  of  the  metal,  and  can  be  rubbed  to  a  polish 
almost  as  bright  as  that  of  the  metal  itself.  Since  in 
addition  to  its  resistance  to  air  it  is  very  light,  it  makes  an 
excellent  material  for  instruments  and  utensils  of  all 
kinds.  Dilute  organic  acids  have  little,  if  any,  solvent 
action  on  aluminium,  but  the  presence  of  sodium  chloride 
is  said  to  increase  the  action.  The  amount  of  soluble 
aluminium  salts  formed  is  however  probably  inconsider- 
able under  any  ordinary  conditions.  Salt  solutions  in 
general  (e.g.  sea-water)  corrode  aluminium  rapidly,  even 
the  small  amount  of  salts  present  in  hard  water  having  a 
corrosive  action.  It  is  dissolved  rapidly  by  alkalies, 
hence  these  should  never  be  used  in  cleaning  aluminium. 
Special  scouring  powders  and  pastes  free  from  alkalies 
may  be  obtained  for  the  purpose,  but  as  a  general  thing 
it  may  be  kept  bright  by  rubbing  dry  after  each  washing 
and  occasionally  wiping  with  a  little  kerosene  oil.  If 
an  ordinary  metal  polish  is  used  care  should  be  taken 
to  remove  every  trace  of  it  from  the  metal. 

Lead,  Pb,  is  largely  used  in  the  arts  on  account  of  the 
ease  with  which  it  can  be  worked  and  soldered.  It 
tarnishes  slightly,  but  only  superficially,  in  moist  air. 
The  organic  acids  of  fruits  and  vegetables  act  upon  it, 
forming  soluble  salts,  which  like  practically  all  com- 
pounds of  lead,  are  poisonous.  Lead  is  an  ingredient  of 


70  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

common  solder,  and  therefore  soldered  utensils  should 
never  be  used  for  cooking  foods  which  may  contain 
acids.  Tin  cans  used  to  be  plated  with  tin  containing 
an  appreciable  amount  of  lead,  and  were  sealed  with  a 
lead  solder.  As  long  as  the  cans  were  air  tight  the  acids 
present  had  no  effect  on  the  lead,  but  when  the  cans  were 
opened  and  the  oxygen  of  the  ah1  had  free  access  lead 
salts  went  into  solution.  For  this  reason  it  was  unsafe 
to  leave  food  standing  in  an  open  can.  Modern  methods 
of  making  and  sealing  cans  have  lessened  the  danger,  but 
it  is  still  wiser  to  take  this  simple  precaution  as  a  general 
rule. 

Lead  has  been  used  for  water  pipes  since  the  days  of 
the  Romans.  Lead  pipe  cannot  be  used  for  soft  water, 
since  this,  by  means  of  the  oxygen  and  carbon  dioxide 
which  it  has  dissolved  from  the  air,  reacts  upon  the  lead, 
forming  compounds  which  dissolve  or  diffuse  through 
the  water  rendering  it  unfit  for  drinking.  Continued 
use  of  water  containing  as  little  as  0.00005  per  cent.,  of 
lead  is  unsafe,  since  lead  compounds  are  excreted  from 
the  system  with  difficulty  and  tend  to  accumulate  to  a 
serious  extent.  Hard  water  has  in  general  less  effect 
on  lead,  and  in  some  cases  where  the  water  supply  of  a 
town  was  found  to  be  acting  on  the  lead  pipes  the 
difficulty  has  been  overcome  by  filtering  the  water 
through  a  bed  of  limestone  or  chalk  to  supply  the 
necessary  hardness.  The  custom  which  prevails  in 
many  parts  of  the  country  of  using  lead-lined  cisterns 
for  the  storage  of  rain  water  is  a  dangerous  one  and  may 
result  in  serious  contamination  of  the  water.  Where 
lead  lined  tanks  must  be  used  they  should  be  well  painted 
on  the  inside  with  a  carbon  paint  and  should  be  frequently 
examined  for  defects  in  the  coating. 

Alloys  are  mixtures  of  two  or  more  metals  which  have 
been  melted  together  and  allowed  to  solidify  into  a  solid 


INORGANIC  CHEMISTRY  71 

mass.  The  physical  properties  of  an  alloy,  such  as 
color,  hardness,  and  melting  point,  are  different  in  many 
cases  from  those  of  the  separate  ingredients,  but  the  in- 
dividual metals  retain  their  chemical  properties  to  a 
large  extent.  In  general  an  alloy  will  melt  lower  than 
a  pure  metal,  and  alloys  made  by  combining  together 
various  metals  which  themselves  have  rather  low  melting 
points  will  melt  in  warm  water.  Low-melting  alloys, 
or  fusible  metals,  as  they  are  called,  are  used  in  making 
fuses  for  electrical  connections.  If  too  strong  a  cur- 
rent is  led  through  the  wires  the  heat  developed  melts 
the  alloy  and  the  circuit  is  broken  before  any  serious 
damage  has  been  done.  Fusible  metal  is  also  used  as 
plugs  in  automatic  sprinklers.  Should  a  fire  start  at 
night  in  an  empty  building  the  heat  melts  the  plugs  of 
the  sprinklers  and  a  deluge  of  water  descends  into  the 
room  below. 

Copper  is  an  ingredient  of  many  alloys.  Brass  is  an 
alloy  of  zinc  and  copper;  bronze  an  alloy  of  copper, 
zinc,  and  tin;  gun  metal  is  tin  and  copper;  "german  silver" 
contains  copper,  zinc,  and  nickel.  In  general,  these 
alloys  should  be  treated  with  the  same  care  as  copper 
itself,  although  the  alloys  are  much  less  liable  to  tarnish- 
ing than  is  the  pure  metal. 


SECTION  II 
ORGANIC  CHEMISTRY 

CHAPTER  XI 
HYDROCARBONS 

The  term  organic  chemistry  was  originally  confined 
to  the  chemistry  of  compounds  which  were  produced 
by  the  vital  activity  of  either  animals  or  plants,  on  the 
supposition  that  such  compounds  differed  essentially 
from  those  which  were  produced  without  the  agency  of 
the  life  force.  When  first  one  and  then  another  of  these 
vital  products  had  been  reproduced  in  the  laboratory 
it  was  recognized  that  this  distinction  must  be  done 
away  with,  but  the  name  " organic"  was  retained  for  the 
vast  number  of  compounds  of  carbon  and  hydrogen, 
with  or  without  other  elements  present,  on  account  of 
the  definite  relations  which  were  found  to  exist  between 
these  substances. 

The  basis  of   organic   chemistry  is  the   tetravalent 

I 

carbon  atom,  which  can  be  pictured  thus,  — C — ,  the 

I 

four  lines  representing  four  valences  which  are  joined 
to  other  atoms.  The  simplest  organic  compound  is 
that  in  which  each  of  these  valences  is  joined  to  a  hydro- 
gen atom.  This  is  the  gas  methane,  the  formula  of  which 
H 

I 
may  be  written  H — C — H,  or,  more  simply,  CH4.     The 


73 


74  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

former  method  of  representation  is  what  is  known  as 
a  graphic  or  structural  formula,  that  is,  a  formula  so 
written  as  to  show  the  exact  arrangement  of  the  four 
valences.  In  a  compound  so  simple  as  methane  this  is 
of  no  consequence,  but  in  more  complex  molecules  it  is 
of  the  greatest  importance.  Organic  chemistry  differs 
materially  from  inorganic  in  this  particular,  that  whereas 
in  inorganic  chemistry  a  formula  stands  for  one  definite 
compound,  among  the  organic  compounds  a  very  large 
number  may  be  represented  by  one  single  formula.  This 
is  due  to  the  great  variety  of  combinations  possible  where 
several  carbon  atoms,  each  with  four  valences,  are  linked 
together.  This  may  be  illustrated  by  the  formula  C4Hi0. 
This  formula  represents  a  compound  containing  four  car- 
bon atoms  and  ten  hydrogen  atoms  in  the  molecule,  but 
experience  shows  that  there  are  actually  two  compounds 
with  distinct  properties  each  having  this  composition. 
On  the  other  hand,  there  is  only  one  CH4,  one  C2H6, 
and  one  C3H8. 

A  study  of  the  structural  formulae  enables  us  to  see  how 
this  may  be  possible.  There  is  only  one  way  in  which  one 
tetravalent  carbon  atom  and  four  monovalent  hydrogen 
atoms  can  be  joined  up  together;  that  is  as  we  have 
written  it.  Nor  can  we  arrange  two  carbons  and  six 
hydrogens,  or  three  carbons  and  eight  hydrogens  in  any 
H  H  H  H  H 

II  111 

but  one  way,  H—  C—  C—  H,  and  H—  C—  C—  C—  H.     But 


four  carbons  and  ten  hydrogens  can  be  linked  together  in 
H    H    H    H 

I       I       I       I 
one  long  chain,  H  —  C  —  C  —  C  —  C  —  H,  or  the  chain  may 


ORGANIC  CHEMISTRY  75 

H 

H— C— H 

H     I     H 


be     branched      H— C— C— C— H.       There     are     the 

I       I       I 
H    H    H 

same  number  of  atoms  in  each  case,  but  they  are  repre- 
sented as  occupying  different  relative  positions  in  space. 
Compounds  like  these,  which  have  the  same  composition 
but  distinct  properties  and  which  are  supposed  to  differ 
only  in  the  relative  positions  of  the  atoms  in  the  mole- 
cule are  called  isomers,  or  isomeric  compounds.  The  num- 
ber of  possible  isomers  increases  very  rapidly  with 
increasing  number  of  carbon  atoms  or  when  other  atoms 
or  groups  of  atoms  are  substituted  for  one  or  more  of  the 
hydrogens  in  the  molecule.  Although  there  is  only  one 
C3H8,  there  are  two  C3H7rs,  namely,  CH3.CH2.CH2I, 
and  CH3.CHI.CH3. 

Compounds  containing  carbon  and  hydrogen  only 
are  grouped  together  into  one  general  class,  the  hydro- 
carbons. A  hydrocarbon  in  which  every  carbon  valence 
is  attached  to  a  separate  atom  or  group  of  atoms, 
as  in  the  formulae  given  above  is  said  to  be  saturated. 
In  an  unsaturated  hydrocarbon  two  carbon  atoms  are 
linked  together  by  two,  or  sometimes  by  three  valences, 
as  in  ethylene,  CH2  =  CH2,  and  acetylene,  CH^CH. 
A  carbon  atom  which  has  more  than  one  of  its  valences 
going  to  any  other  atom  is  said  to  be  unsaturated. 
Unsaturation  is  always  characterized  by  great  reactivity. 
The  double  and  triple  bonds,  as  they  are  called,  readily 
separate,  adding  on  other  atoms  to  form  a  saturated 
compound.  The  saturated  compounds  cannot  undergo 
addition  reactions,  and  react  only  by  substitution,  by 


76  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

0 

exchanging  one  of  the  atoms  already  present  in  the  mole- 
cule for  some  other  atom. 

Paraffins  are  hydrocarbons  composed  of  open  chains 
of  saturated  carbon  atoms.  Chemically  they  are  very 
inert,  reacting  only  with  the  halogens,  Cl,  Br,  and  I, 
with  which  they  give  halogen  substitution  products  in 
which  one,  two,  or  more  hydrogens  are  replaced  by 
halogen  atoms.  Taking  the  reaction  of  methane  with 
bromine  as  typical,  under  suitable  conditions  the  reaction 
proceeds  as  follows: 

CH4  +  Br2  =  CH3Br  +  HBr. 

In  presence  of  excess  of  bromine  the  reaction  may  be 
carried  further  until  all  four  H's  have  been  successively 
replaced. 

CH3Br  +  Br2  =  CH2Br2  +  HBr. 

CH2Br2  +  Br2  -  CHBr3  +  HBr. 
CHBr3  +  Br2  =  CBr4  +  HBr, 

Some  of  these  halogen  substitution  products  are  of 
practical  importance.  CHC13  is  the  valuable  anaesthetic 
chloroform;  the  corresponding  iodine  compound,  CHI3, 
is  an  antiseptic,  iodoform;  CC14,  carbon  tetrachlonde 
is  an  excellent  solvent  for  fats  and  has  found  considerable 
use  as  a  cleansing  agent,  being  sold  for  this  Durpose  under 
the  trade  name  carbona. 

Although  the  group  of  paraffins  includes  various 
substances  in  common  use,  such  as  gasoline,  kerosene, 
benzine,  and  other  cleansing  fluids,  and  many  lubricating 
oils,  their  chief  interest  from  the  chemist's  point  of  view 
lies  in  the  fact  that  they  are  the  parent  substances  of  an 
almost  infinite  number  of  derivatives,  to  which  is  given 
the  general  name  of  aliphatic  compounds.  While  the 
paraffins  do  not  react  directly  with  anything  except  the 


ORGANIC  CHEMISTRY  77 

halogens,  the  halogen  derivatives  thus  formed  are  more 
reactive,  and  it  is  possible  to  substitute  for  the  halogen 
almost  any  desired  atom  or  group  of  atoms.  In  this 
way  are  derived  a  great  many  different  classes  of  aliphatic 
compounds,  many  of  them  somewhat  resembling  the 
various  types  of  inorganic  compounds,  oxides,  hydroxides, 
acids,  and  so  on,  but  differing  essentially  from  these  in 
many  of  their  properties  and  reactions.  Only  a  few  of 
these  classes,  and  only  one  or  two  of  the  more  important 
members  of  each  class  will  be  considered  here.  It  is  to 
be  remembered  that,  with  the  exception  of  a  few  minor 
peculiarities,  what  is  true  of  one  individual  substance  is 
true  of  the  whole  class  to  which  it  belongs.  It  is  there- 
fore only  necessary  to  learn  a  few  general  facts  which 
may  easily  be  kept  in  mind,  without  burdening  the 
memory  with  a  mass  of  detail. 

The  residue  which  would  be  left  if  we  took  one  hydro- 
gen from  a  paraffin  is  called  an  alkyl  group,  or  alkyl 
radicle.  An  alkyl  group  cannot  exist  by  itself  since  it 
would  have  a  valence  unsatisfied,  but  all  aliphatic 
compounds  except  the  paraffins  themselves  may  be 
considered  alkyl  derivatives.  In  the  various  reactions 
in  which  these  derivatives  take  part  the  alkyl  group 
remains  for  the  most  part  unchanged,  behaving  like  a 
single  unit.  Halogens  are  the  only  reagents  which 
affect  the  alkyl  group,  and  they  may  be  made  to  react 
with  it  as  they  do  with  the  paraffins  themselves,  giving 
halogen-substituted  groups.  The  individual  alkyl 
groups  are  named  as  follows:  CH3,  methyl;  C2H5,  ethyl; 
C3H7,  propyl;  C4H9,  butyl;  C5Hn,  amyl;  and  all  others 
by  adding  the  suffix  -yl  to  the  stem  of  the  Greek  numeral 
indicating  the  number  of  carbon  atoms  which  they 
contain,  hexyl,  heptyl}  octyl,  etc.  Addition  of  one 
hydrogen  to  an  alkyl  group  gives  the  corresponding 
paraffin,  which  is  named  by  substituting  the  ending 


78  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

-ane  for  the  -yl  of  the  alkyl  group;  thus  CH4  is  methane, 
C2H6,  ethane ,  C3H8,  propane,  etc. 

It  is  to  be  noted  that  the  various  alkyl  groups,  and, 
similarly,  the  various  paraffins,  differ  from  each  other  in 
composition  only  by  addition  or  subtraction  of  CH2 
or  a  multiple  of  this.  Any  series  of  compounds  in  which 
the  members  differ  by  this  regular  progression  is  called 
a  homologous  series.  The  members  of  a  homologous 
series  resemble  each  other  very  closely  in  chemical 
properties,  differing  only  in  degree  of  reactivity,  the  lower 
members,  i.e.  those  with  fewer  carbon  atoms,  being  in 
general  slightly  more  reactive  than  the  higher  members. 
In  physical  properties  a  regular  gradation  may  be 
observed,  the  lower  members  being  as  a  rule  more  volatile 
and  more  soluble  than  the  higher.  The  lower  members 
of  any  series  are  apt  to  be  gases  or  liquids,  the  higher 
members  solid. 


CHAPTER  XII 

ALCOHOLS  AND  ETHERS 

If  one  hydrogen  in  a  paraffin  is  replaced  by  an  hydroxyl 
group  the  resulting  compound  is  an  alcohol.  The 
alcohol  molecule  may  therefore  be  regarded  as  composed 
of  an  alkyl  group  and  an  hydroxyl  group,  the  latter 
giving  to  the  molecule  its  characteristic  properties. 
The  simplest  member 'of  the  series  of  alcohols  would  be 
CH3OH;  the  next  higher  member,  according  to  our 
definition  of  homologous  series,  would  be  C2H5OH,  the 
next  C3H7OH,  etc.  These  compounds  are  named  from 
the  alkyl  group  which  they  contain,  methyl,  ethyl, 
propyl,  etc.,  alcohols.  An  alcohol  containing  only  one 
hydroxyl  group  in  the  molecule  is  called  monohydric; 
those  containing  two  or  more  hydroxyls  are  called  poly- 
hydric.  The  most  important  polyhydric  alcohol  is  glyc- 
erine, C3H5(OH)3,  derived  from  propane  by  replacing 
one  of  the  H's  attached  to  each  C  by  OH;  so  from 
CH3.CH2.CH3  is  derived  CH2OH.CHOH.CH2OH. 

In  general  the  alcohols  are  colorless  liquids,  although 
a  few  of  the  higher  members  are  solid.  The  liquid 
members  are  good  solvents  for  almost  all  kinds  of  organic 
compounds,  and  for  that  reason  play  an  important  part 
in  a  great  number  of  very  diverse  organic  reactions. 
Moreover,  in  virtue  of  the  reactivity  of  the  hydroxyl 
group  they  are  used  in  many  reactions  for  the  purpose 
of  introducing  either  an  alkyl  or  an  alkoxyl  (-OCH3, 
-OC2H5,  etc.)  group  into  a  molecule. 

Methyl  alcohol,  CH3OH,  is  sometimes  called  wood 
spirit  because  it  is  one  of  the  principle  products  obtained 

79 


80  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

when  wood  is  heated  to  a  high  temperature  in  a  retort 
out  of  contact  with  air.  Because  of  this  very  cheap 
method  of  production  methyl  alcohol  is  the  cheapest  of 
the  alcohols,  and  since  it  is  as  good  a  solvent  for  most 
purposes  as  the  more  costly  ethyl  alcohol  it  was  formerly 
used  very  extensively  in  manufactures.  Unfortunately 
it  is  extremely  poisonous,  acting  not  only  when  taken 
into  the  system  through  the  mouth,  but  even  when 
absorbed  through  the  skin  or  the  lungs.  Workmen 
engaged  in  the  manufactures  in  which  methyl  alcohol 
was  extensively  used  suffered  severely  from  general 
debility,  followed  in  many  cases  by  partial  or  even 
complete  blindness  and  paralysis.  Pure  ethyl  alcohol 
on  the  other  hand  is  too  expensive  for  most  industrial 
uses,  as  in  addition  to  the  cost  of  making  there  is  a 
heavy  Government  tax  imposed  on  all  alcohol  which  can 
be  used  as  a  beverage.  Denatured  alcohol  is  ethyl 
alcohol  to  which  has  been  added  some  other  substance 
with  a  disagreeable  taste  and  smell  but  which  will  not 
affect  its  use  for  industrial  purposes.  Such  alcohol  is 
tax  free,  and  sufficiently  cheap  to  enable  the  manufac- 
turer to  substitute  it  in  almost  every  case  for  the  dis- 
agreeable and  dangerous  methyl  alcohol.  The  first 
denaturant  used  was  10  per  cent,  methyl  alcohol,  the 
mixture  being  sold  as  methylated  spirit;  later  an  alternative 
denaturant,  2  per  cent,  methyl  alcohol  and  0.5  per  cent, 
of  certain  pyridine  bases,  was  permitted  by  the  Govern- 
ment. Since  1917  alcohol  for  external  medical  use  has 
been  denatured  by  the  addition  of  a  small  amount  of 
carbolic  acid.  This  is  a  poison  when  taken  internally, 
but  was  formerly  much  used  as  an  antiseptic,  although 
it  has  fallen  somewhat  into  disrepute  of  late  years. 

Ethyl  alcohol,  the  alcohol  of  common  usage,  is  pre- 
pared by  fermentation  from  the  starch  present  in  grain 
and  potatoes  or  the  sugar  in  fruit  juices,  a  process  to 


ORGANIC  CHEMISTRY  81 

be  described  later.  When  denatured  it  is  used  as  a 
solvent,  as  a  reagent  for  industrial  purposes,  and  to  some 
extent  as  a  fuel.  When  diluted  with  water  and  flavoring 
extracts  it  is  used  as  a  beverage.  Whiskey  is  grain 
alcohol  flavored  by  the  extractives  from  the  grain, 
and  contains  about  40  per  cent,  alcohol.  Brandy  is  the 
spirit  obtained  by  distillation  of  wine,  and  usually  con- 
tains from  40  to  50  per  cent,  alcohol.  Rum  is  made  by 
distilling  the  product  obtained  by  fermenting  molasses, 
and  contains  about  50  per  cent,  alcohol.  Wines  are 
made  from  fruit  juices,  and  contain  from  7  to  16  per 
cent,  alcohol.  The  various  beers  are  made  from  barley 
and  contain,  along  with  from  2  to  4  per  cent,  of  alcohol, 
various  extractives  from  the  barley  grain,  to  which 
they  doubtless  owe  their  tonic  properties. 

In  propyl  alcohol  we  find  the  possibility  of  isomerism 
among  the  alcohols.  There  are  two  possible  propyl 
alcohols,  one  of  which  has  the  hydroxyl  at  the  end  of  the 
chain,  CH3.CH2.CH2OH,  and  one  in  which  it  is  in  the 
middle,  CH3.CHOH.CH3.  An  alcohol  in  which  the 
hydroxyl  is  attached  to  a  carbon  atom  which  is  directly 
joined  to  only  one  other  carbon  as  in  the  first  of  the  two 
formulae  given  above,  is  called  a  primary  alcohol; 
one  in  which  the  hydrogen  is  attached  to  a  carbon  atom 
which  is  directly  joined  to  two  other  carbons,  as  in  the 
second  formula,  is  called  a  secondary  alcohol;  while 
one  in  which  the  hydroxyl  is  attached  to  a  carbon  which 
is  directly  joined  to  three  other  carbons  is  called  a 

CH3 

I 
tertiary  alcohol,  e.g.  tertiary  butyl  alcohol,  CH3 — C — OH 

CH3 

Ethers. — As  the  alcohols  with  their  OH  group  cor- 
respond more  or  less  to  inorganic  bases,  so  the  ethers  may 


82  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

be  considered  analogous  to  inorganic  oxides.  The  general 
formula  of  the  ethers  may  be  written  R — O — Ri,  where 
R  and  Ri  represent  alkyl  groups.  They  are  derived 
from  the  alcohols  by  substituting  a  second  alkyl  group 
for  the  H  of  the  OH.  The  anaesthetic  known  as  ether, 
or  sometimes  sulphuric  ether  (from  the  fact  that  sulphuric 
acid  is  used  in  its  preparation),  is  ethyl  ether,  C2H5— 
O— C2H5. 

Ether  is  an  excellent  solvent  for  most  organic  sub- 
stances. It  mixes  readily  with  alcohol  in  all  proportions 
but  is  almost  insoluble  in  water.  When  it  is  necessary 
to  cleanse  the  hands  thoroughly  for  surgical  work  they 
are  washed  first  with  soap  and  water  to  take  off  the  dirt 
particles,  then  with  alcohol,  which  mixes  with  and 
removes  the  last  traces  of  moisture  and  soap,  and  then 
finally  with  ether  to  dissolve  away  the  closely  adhering 
film  of  grease  which  is  present  on  all  normal  skin.  Were 
it  not  for  the  intermediate  treatment  with  alcohol  the 
ether  would  not  be  able  to  penetrate  into  the  pores  and 
crevices  of  the  skin,  while  alcohol  alone  would  be  a  much 
less  efficient  cleansing  agent. 


CHAPTER  XIII 
ALDEHYDES  AND  KETONES 

Alcohols  are  fairly  susceptible  to  oxidizing  agents, 
the  lower  members  being  the  most  easily  oxidized.  The 
product  of  oxidation  depends  upon  the  position  of  the 
hydroxyl  group.  Oxidation  of  a  primary  alcohol  produces 
an  aldehyde,  with  loss  of  two  atoms  of  hydrogen  which 
are  oxidized  to  water.  In  the  case  of  methyl  alcohol 
the  reaction  may  be  written  thus  : 

H  H 

I  I 

H—  C—OH  +  O  =  H—  C  =  O  +  H2O 


Similarly  in  the  case  of  ethyl  alcohol, 
H  H 

CH3—  C—  OH  +  O  =  CH3—  C  =  O  +  H2O 


or,  in  general,  if  we  use  R  to  represent  any  alkyl  group, 
H  H 


R— C— OH  +  O  =  R— C  =  O  +  H20 
H 


H 


The  aldehydes  are  characterized  by  the  group  — C  =  O, 
the  fourth  valence  of  the  carbon  being  satisfied  by  any 

83 


84  CHEMISTRY  FOB  NURSES  AND  STUDENTS 

alkyl  group,   or  in  the  case  of  the  aldehyde    derived 
from  methyl  alcohol,  by  another  hydrogen. 

When  a  secondary  alcohol  is  oxidized  the  reaction  is 
exactly  similar,  but  the  product  in  this  case  is  called  a 
R  R 

I  I 

ketone,  R  —  C  --  OH  +  O  =  R  —  C  =  O  -f  H2O 


Ketones  are  characterized  by  the  group  >C  =  O, 
both  remaining  valences  of  the  carbon  being  satisfied  by 
alkyl  groups. 

Tertiary  alcohols  are  oxidized  only  with  great  dif- 
ficulty, and  the  process  results  in  complete  rupture  of  the 
molecule. 

It  will  be  noted  that  the  grouping  >  C  =  O  is  common 
'to  both  aldehydes  and  ketones,  the  difference  being 
that  in  the  case  of  the  aldehydes  at  least  one  of  the  re- 
maining valences  is  satisfied  by  hydrogen,  while  in  the 
ketones  they  are  both  attached  to  alkyl  groups.  This 
>C  =  O  grouping  is  called  the  carbonyl  group,  and  is 
characterized  by  great  reactivity,  which  is  increased  by 
the  presence  of  hydrogen  attached  to  the  carbon  of 
the  carbonyl  group.  For  this  reason,  while  aldehydes 
and  ketones  are  both  reactive  the  aldehydes  are  much 
more  so.  For  the  most  part  they  undergo  the  same 
reactions,  but  in  the  case  of  the  aldehydes  the  reaction 
is  more  easily  brought  about 

Aldehydes  are  very  readily  oxidized  further,  the  H 
being  oxidized  to  an  OH. 

H  OH 

I  I 

R— C  =  O  +  O  =  R— C  «  O 

On  account  of  the  great  ease  with  which  this  reaction 
takes  place  aldehydes  are  good  reducing  agents.  Certain 


ORGANIC  CHEMISTRY  85 

metallic  oxides  will  give  up  their  oxygen  to  the  aldenydes, 
themselves  becoming  reduced  to  the  metal.  This  has 
become  the  basis  of  a  simple  test  for  an  aldehyde, 
copper  being  the  metal  most  commonly  used  for  the 
purpose.  In  the  presence  of  an  aldehyde  a  solution  of 
cupric  oxide  is  reduced  to  cuprous  oxide,  which  forms  a 
dark  red  precipitate. 

H  OH 

I  .  I 

R— C  =  0  +  2CuO  =  R— C  ==O  +  Cu2O 

Since  ketones  have  no  hydrogen  attached  to  the  car- 
bonyl  carbon,  oxidation  can  take  place  only  by  rupture 
of  the  chain.  Thus  from  the  simplest  ketone,  acetone, 

OH 

I 

CH3.CO.CH3,  we  obtain  on  oxidation  CH3— C  =  O, 
CO2,  and  H2O.  As  might  be  expected,  ketones  are 
less  readily  oxidized  than  are  the  aldehydes. 

Formaldehyde,  H.CHO,  the  first  member  of  the  alde- 
hyde series,  is  produced  by  the  oxidation  of  methyl 
alcohol.  It  is  a  gas  with  a  very  pungent  odor,  which  is 
largely  used  as  a  disinfectant.  A  40  per  cent,  solution 
of  the  gas  in  water  is  sold  under  the  trade-name  Formalin. 
Formaldehyde  molecules  have  a  tendency  to  combine 
together  into  a  complex  molecule  of  which  the  exact 
structure  is  unknown.  The  formaldehyde  candles  which 
are  used  in  disinfecting  are  composed  of  this  formalde- 
hyde complex,  or  paraformaldehyde,  as  it  is  called.  When 
they  are  lighted  the  heat  from  the  burning  wick  causes 
the  disintegration  of  the  complex  into  the  simple  form. 
Formaldehyde  acts  on  micro-organisms  by  combining 
with  their  protoplasm  and  preventing  it  from  functioning. 


CHAPTER  XIV 
ACIDS 

Organic  acids,  like  inorganic,  owe  their  acid  properties 
to  hydrogen  ions,  but  not  all  the  hydrogen  of  organic 
acids  is  ionized.  The  H  of  the  -OH  group  as  found 
in  the  alcohols  is  non-ionizable,  as  is  the  H  attached  to 
the  — CO  group  in  the  aldehydes.  When  an  OH  and  a 
doubly  bound  O  are  attached  to  the  same  C  however, 
as  is  seen  in  the  oxidation  products  of  the  aldehydes,  the 
H  becomes  ionizable  and  the  compound  shows  all  the 

OH 

I 
properties   of   an   acid.     The   grouping   — C  =  O,    (or 

— COOH  as  it  is  oftener  written),  is  called  the  carboxyl 
group,  and  is  characteristic  of  the  organic  acids. 

Acids  are  produced  as  the  final  oxidation  products  of 
the  alcohols,  aldehydes,  or  ketones.  Those  in  most 
common  use,  however,  are  more  frequently  obtained  as 
products  of  the  vital  activity  of  animals  or  plants.  The 
souring  of  milk,  wine,  bread,  and  many  other  food 
substances,  is  due  to  the  production  of  acid  through 
the  agency  of  bacteria.  Acetic  acid,  CH3.COOH,  is 
obtained  by  oxidation  of  ethyl  alcohol,  the  corresponding 
aldehyde  being  an  intermediate  product.  This  oxida- 
tion may  be  brought  about  by  ordinary  chemical  means 
or  by  the  action  of  the  bacillus  Mycoderma  aceti.  Since 
this  bacillus  is  very  commonly  present  in  the  air,  on  the 
skins  of  fruit,  etc.  acetic  acid  is  produced  whenever  a 
dilute  solution  of  alcohol,  along  with  some  nitrogenous 
material  to  serve  as  food  for  the  micro-organisms,  is 

86 


ORGANIC  CHEMISTRY  87 

left  exposed  to  the  air.  If  there  is  more  than  about 
10  per  cent,  of  alcohol  present  however  the  bacteria  will 
not  flourish  and  the  souring  is  prevented.  Ordinary 
vinegar  is  a  solution  of  acetic  acid  produced  in  this  way, 
containing  3-6  per  cent,  of  acid  together  with  flavoring 
material  from  the  fruit  or  grain  extract  used  for  ferment- 
ing. The  name  vinegar,  without  qualification,  is  used  in 
the  United  States  for  the  product  made  from  apple  juice 
or  cider  only,  but  vinegar  may  also  be  made  from  beer 
(malt  vinegar),  wine  (white  wine  vinegar),  or  molasses. 
Acetic  acid  is  also  obtained,  along  with  methyl  alcohol, 
when  wood  is  destructively  distilled,  and  it  is  in  this 
way  that  most  of  the  acetic  acid  used  industrially  is 
obtained. 

The  acid  produced  when  milk  sours  is  lactic  acid, 
CH3.CHOH.COOH.  This  acid  has  a  hydroxyl  group 
in  the  molecule  as  well  as  a  carboxyl,  and  therefore  shows 
some  of  the  properties  of  an  alcohol  as  well  as  those-  of 
an  acid.  Tartaric  acid,  present  in  the  form  of  its  sodium- 
potassium  salt  in  grape  juice,  from  which  it  is  extracted 
and  sold  as  cream-of-tartar,  contains  two  hydroxyl  and 
two  carboxyl  groups,  COOH.CHOH.CHOH.COOH. 
Citric  acid,  to  which  oranges  and  lemons  owe  their 
sour  taste,  has  one  hydroxyl  and  three  carboxyl  groups. 

Organic  acids  are  neutralized  by  inorganic  bases,  form- 
ing salts, 

CH3.COOH  +  NaOH  =  CH3COONa  +  H2O. 

A  dicarboxylic  acid,  such  as  tartaric,  takes  two  molecules 
of  base  for  neutralization ;  a  tricarboxylic  acid  takes  three 
molecules  of  base. 

COOH.CHOH.CHOH.COOH  +  2    NaOH  - 
COONa.CHOH.CHOH.COONa  +  H2O. 

Here  the  hydroxyl,  being  alcoholic  in  its  nature,  is  un- 
acted upon  by  the  base. 


88  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

The  salts  are  named  by  adding  the  termination  -ate 
to  the  stem  of  the  name  of  the  acid.  The  salts  of  acetic 
acid  are  known  as  acetates;  of  propionic  acid,  prop- 
ionates;  of  tartaric  acid,  tartrates,  and  so  on.  The 
sodium  salt  of  acetic  acid  is  sodium  acetate,  the  potassium 
salt  potassium  acetate,  etc. 


CHAPTER  XV 

ESTERS 

Just  as  the  organic^ jacids  rejicj.  jmtliSjkases  to  form 
iey  react"  with  alcohols  to  form  compounds  known 
as  esters. 

CH3.COOH  +  C2H5OH  =  CH3.COOC2H6  +  H2O. 
The  esters  correspond  to  salts,  with  an  alkyl  group 
taking  the  place  of  the  metal  of  the  salt.  They  are 
named  like  the  salts  with  the  name  of  the  alkyl  group 
of  the  alcohol  written  in  place  of  that  of  a  metal.  So 
the  ester  given  above  is  ethyl  acetate.  If  methyl  alcohol 
had  been  used  instead  of  ethyl  alcohol  the  resulting 
product  would  have  the  formula  CH3.COOCH3,  and 
would  be  called  methyl  acetate.  If  formic  acid  were 
substituted  for  acetic  we  would  get  methyl  or  ethyl 
formate,  according  to  the  alcohol  employed.  The  esters 
are  for  the  most  part  pleasant  smelling  liquids.  The 
characteristic  flavors  of  many  fruits  are  due  to  the  esters 
which  they  contain. 

Under  suitable  conditions  an  ester  will  take  up  a 
molecule  of  water  and  reform  the  acid  and  alcohol  from 
which  it  was  derived. 

CH3.COOC2H5  +  H20  =  CH3COOH  +  C2H5OH. 

This  reaction  is  known  as  hydrolysis,1  or  saponification, 
and  may  be  brought  about  by  steam  at  high  temperature, 
by~alkalies,  which  combine  with  the  acid  as  soon  as 
produced  to  form  a  salt,  or  by  the  aid  of  small  quantities 
of  inorganic  acids  (H2S04  or  HC1),  or  by  enzymes, 
which  act  as  catalysts. 

1  See  page  24. 

89 


90  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

More  important  than  the  simple  esters,  from  a  physio- 
logical standpoint,  are  the  fats.  Fats  are  esters  of  the 
polyhydric  alcohol  glycerine.  As  this  alcohol  has  three 
hydroxyl  groups  it  reacts  with  three  molecules  of  acid. 
If  these  three  molecules  are  all  of  the  same  acid  we 
have  a  simple  fat,  whereas  if  they  are  different  we  have  a 
mixed  fat.  If  we  represent  any  acid  by  R.COOH 
the  reaction  between  this  and  glycerine  to  produce  a 
fat  will  be  written  thus: 

Glycerine         Acid  Fat 

CH2OH  CH2OOC.R. 

I  1 

CHOH   -j-  3R.COOH  =  CHOOC.R  +  3H2O. 

I  I 

CH2OH  CH2OOC.R. 

The  most  important  fats  are  those  produced  by  the 
interaction  of  glycerine  and  palmitic,  stearic,  and  oleic 
acids.  Palmitic  and  stearic  acids  have  the  formulae 
C15H3i.COOH  and  Ci7H35.COOH  respectively,  and  be- 
long to  the  same  series  as  acetic  acid.  Oleic,  Ci7H33.- 
COOH,  is  an  unsaturated  acid  with  a  double  bond  in  its 
carbon  chain.  It  has  a  lower  melting  point  than  the 
corresponding  saturated  acids,  as  is  usually  the  case 
with  unsaturated  as  compared  with  saturated  com- 
pounds. For  this  reason  fats  in  which  the  ester  of 
oleic  acid  predominates  are  liquid,  while  those  which  are 
rich  in  palmitate  or  stearate  are  solid.  Vegetable 
fats  are  usually  rich  in  oleic  ester,  olive  oil  being  about 
95  per  cent,  of  this  fat,  while  animal  fats  contain  a 
larger  proportion  of  palmitate  and  stearate.  The  pro- 
portions differ  somewhat  in  different  species  and  even 
in  different  animals  of  the  same  species.  The  fat  of 
cold-blooded  animals  is  higher  in  oleate,  and  consequently 
lower-melting,  than  that  of  warm-blooded  animals. 


ORGANIC  CHEMISTRY  91 

Pork  fat  contains  about  67  per  cent,  oleic  ester,  human 
fat  about  the  same  amount,  beef  and  mutton  fat  less. 
When  a  fat  is  hydrolyzed,  or  saponified,  by  sodium 
or  potassium  hydroxide  the  products  are  glycerine  and 
the  sodium  or  potassium  salts  of  the  fatty  acids. 

CH2OOC.R  CH2OH. 

i 

CHOOC.R   +  SNaOH  =  CHOH  +  SR.COONa. 

I  I 

CH2OOC.R  CH2OH. 

These  salts  are  soaps.  Properly  speaking  any  salt  of 
palmitic,  stearic,  or  oleic  acid  is  a  soap,  but  the  term  is 
ordinarily  restricted  to  the  potassium  and  sodium  salts, 
which  are  soluble  in  water,  while  all  others  (with  the 
exception  of  the  ammonium  salts)  are  insoluble.  Potas- 
sium salts  are  called  soft  soaps  and  sodium  salts  are 
hard  soaps,  although  these  terms  are  only  relative,  the 
hardness  or  softness  depending  also,  to  a  certain  extent 
at  least,  upon  the  amount  of  water  left  in  the  soap  in 
the  process  of  making.  In  homemade  soaps  and  some 
varieties  of  commercial  soap  the  glycerine  is  left  in  the 
soap,  but  more  generally  it  is  separated  and  saved, 
as  it  is  a  very  valuable  by-product,  serving  as  the  basis 
for  many  of  our  modern  explosives. 

Various  theories  have  been  put  forward  to  account 
for  the  cleansing  action  of  soap,  of  which  only  the  one 
or  two  which  appear  to  be  most  satisfactory  will  be 
mentioned  here.  According  to  the  emulsification  theory 
dirt  is  held  to  a  dirty  object  by  a  thin  layer  of  grease. 
Soap  cleanses  by  emulsifying  the  grease,  whereupon 
the  dirt,  no  longer  having  anything  to  which  to  adhere, 
falls  away.  Doubtless  this  emulsification  plays  a  part, 
possibly  an  important  part,  in  the  cleansing  effect  of 
soap.  That  it  is  not  the  whole  explanation  is  proved  by 


92  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

experiments  which  showed  that  filter  paper  could  be  soiled 
by  a  suspension  of  lamp-black  in  water  even  when  all 
grease  had  been  carefully  removed,  while  no  soiling  took 
place  if  soap  were  added  to  the  water  in  which  the  lamp- 
black was  suspended.  To  account  for  this  it  has  been 
suggested  that  a  combination  of  some  kind  occurs  be- 
tween the  dirt  and  the  object,  and  this  is  decomposed 
by  the  soap,  which  itself  combines  with  the  dirt,  forming 
a  soluble  compound  which  is  washed  away.  It  is  prob- 
able that  no  one  theory  is  sufficient  to  explain  the  action  of 
soap,  but  it  may  be  that  there  is  a  combination  of  these 
two  actions,  possibly  with  some  other  as  well. 

When  soap  is  added  to  "  hard  "  water  a  curdy  substance 
separates  on  the  surface  of  the  water,  and  no  lather  can 
be  obtained  until  a  large  amount  of  soap  has  been  added. 
This  curd  is  a  compound  formed  by  the  interaction  of  the 
soap  with  soluble  calcium  or  magnesium  salts  which  are 
present  in  the  water. 

2R.COONa  +  Ca(HCO3)2  =  (R.COO)2Ca  +  NaHCO3. 
SR.COONa  +  MgCl2  =  (R.COO)2Mg  +  2  NaCl. 

Not  until  all  the  calcium  and  magnesium  salts  have  been 
removed  from  the  solution  can  the  soap  exert  its  normal 
effect. 

Since  this  action  represents  a  considerable  waste  of 
soap,  besides  the  formation  of  a  disagreeable  curd  which 
is  apt  to  stick  to  and  stain  clothes,  utensils,  etc.,  it  is 
highly  desirable  that  the  salts  to  which  it  is  due  should 
be  removed  from  the  water  before  it  is  used  for  washing. 
This  is  what  is  known  as  " softening"  water,  and  may  be 
brought  about  in  various  ways  according  to  the  cause  of 
the  hardness. 

Where  the  objectionable  salt  is  calcium  acid  carbonate, 
as  is  frequently  the  case,  it  can  be  rendered  insoluble, 
and  therefore  harmless,  by  boiling  the  water.  Soluble 


ORGANIC  CHEMISTRY  93 

calcium  acid  carbonate  is  converted  by  heat  into  in- 
soluble calcium  carbonate,  water  and  carbon  dioxide 
being  given  off.  (Compare  the  behavior  of  sodium 
acid  carbonate,  page  21). 

Ca(HCO3)2  ==  CaCO3  +  H2O  +  CO2. 

The  scale  which  often  forms  inside  a  tea  kettle  is  a 
deposit  of  calcium  carbonate  which  has  been  precipitated 
from  the  water  in  this  way. 

Water  which  can  be  softened  by  boiling  is  said  to 
have  temporary  hardness.  If  the  hardness  is  due  to 
calcium  or  magnesium  chloride  or  sulphate  it  is  said 
to  have  permanent  hardness  and  boiling  has  no  effect. 
These  salts  must  be  removed  by  precipitation  with  some 
other  reagent.  For  household  use  the  most  satisfactory 
reagent  for  this  purpose  is  sodium  carbonate,  (washing 
soda),  which  reacts  to  form  the  insoluble  carbonates 
of  calcium  and  magnesium  along  with  soluble  sodium 
salts  which  are  harmless. 

Na2CO3  +  CaCl2  =  CaCO3  +  2NaCl. 

Na2CO3  +  MgCl2  =  MgCO3  +  2NaCl. 

Na2CO3  +  Ca(HCO3)2  =  CaC03  +  2NaHCO3. 

Too  large  an  excess  of  washing  soda  in  the  water 
should  be  avoided  as  it  is  injurious  to  fabrics,  and  indeed 
for  most  purposes.  Its  use  in  moderation,  however, 
results  in  many  cases  in  a  very  considerable  saving. 
Different  waters  vary  considerably  in  their  hardness, 
the  degree  of  hardness  of  any  particular  water  being 
determined  by  the  amount  of  standard  soap  solu- 
tion which  must  be  added  to  it  before  a  lather  will  form. 
It  is  not  uncommon  to  find  water  which  uses  up  20-40 
ounces  of  soap  per  100  gallons  of  water  before  any  lather 
can  be  obtained,  and  if  we  allow  the  moderate  estimate 


94  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

of  10  gallons  of  water  per  person  per  day  this  would 
require  from  50  to  100  pounds  of  soap  per  person  per 
year  for  each  person  in  the  family.  Paying  at  the  present 
retail  price  of  20  cents  a  pound,  a  family  of  five  would 
spend  about  $50.00  a  year  on  the  extra  soap  required  to 
soften  their  water.  Washing  soda,  on  the  other  hand,  is 
about  three  times  as  efficient  as  soap  for  this  purpose, 
so  that  17  pounds  of  washing  soda  at  3  cents  a  pound 
would  effect  as  much  as  50  pounds  of  soap  at  about  one- 
twentieth  the  cost. 

Where  possible,  it  is  well  worth  while  having  the 
water  tested  in  order  to  find  out  the  degree  of  hardness, 
and  therefore  the  amount  of  soap  and  soda  respectively 
required  to  soften  it. 


CHAPTER  XVI 

CARBOHYDRATES 

The  carbohydrates  are  a  very  important  class  from  a 
physiological  standpoint,  because  so  many  of  our  im- 
portant foodstuffs  belong  to  this  class.  Carbohydrates 
contain  an  aldehydic  or  ketonic  group  attached  to  the 
last  or  the  last  but  one  carbon  of  a  chain  of  carbon 
atoms  each  of  which  carries  a  hydroxyl  group.  Sugars 
are  carbohydrates  with  a  sweet  taste.  The  carbohy- 
drates are  classified  in  groups  according  to  the  number 
of  carbons  which  they  contain.  A  biose  has  two  carbon 
atoms,  a  triose  three,  a  tetrose  four,  and  so  on,  up  to  the 
nonoses  with  nine.  Of  these  the  hexoses,  C6Hi206,  are 
by  far  the  most  important. 

Among  the  carbohydrates  there  are  a  great  many 
possibilities  of  isomerism,  as  will  be  seen  from  a  considera- 
tion of  the  structural  formulae.  If  we  consider  the 
simplest  carbohydrate,  biose,  there  is  only  one  possible 
arrangement  of  atoms  which  will  answer  the  definition 
of  a  carbohydrate,  CH2OH.CHO,  but  we  can  have  two 
trioses,  an  aldehydic  or  a  ketonic  derivative,  CH2OH. 
CHOH.CHO,  and  CH2OH.CO.CH2OH.  When  we  come 
to  the  tetroses  still  further  variation  is  possible.  Not 
only  may  we  have  an  aldehydic  and  a  ketonic  derivative, 
but  if  we  write  the  formulae  of  these  in  such  a  way  as  to 
indicate  the  relative  positions  of  the  various  atoms  in  the 
molecule  it  will  be  seen  that  we  must  have  different 
isomers  according  as  the  hydroxyls  lie  adjacent  to  each 
other  or  farther  apart  in  the  molecule. 

95 


96  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

CH2OH  CH2OH 

I  I 

H— C— OH  OH— C— H 

and  | 

H— C— OH  H— C— OH 

I  I 

H— C  =  0  H-C  =  0 

The  number  of  possible  isomers  increases  very  rapidly 
with  increase  in  the  number  of  carbon  atoms  in  the 
chain,  but  comparatively  few  of  these  are  of  practical 
importance. 

Carbohydrates  with  the  general  formula  CnH2nOn 
are  known  as  monosaccharides.  This  includes  all  the 
sugars  from  biose  up  to  the  nonoses.  Three  of  these, 
all  hexoses,  are  important  food  substances,  glucose 
(also  called  dextrose  or  grape  sugar),  fructose  (Icevulose 
or  fruit  sugar),  and  galactose.  Glucose  and  fructose 
differ  only  in  being  aldehydic  and  ketonic  respectively, 
while  galactose  is  aldehydic  and  differs  from  glucose  in 
the  relative  arrangement  of  the  H's  and  OH's  in  the 
carbon  chain.  Glucose  is  found  in  most  fruits  and  some 
vegetables,  and  may  be  made  from  starch  by  a  method 
to  be  discussed  later.  It  is  the  component  to  which 
corn  syrup  owes  its  sweetness,  having  been  formed 
from  the  starch  of  the  corn.  Fructose  is  also  present 
in  many  fruits,  but  in  smaller  quantity  than  glucose  for 
the  most  part.  A  considerable  amount  of  this  sugar 
is  present  in  honey.  Galactose  is  obtained  from  milk 
sugar. 

Disaccharides  are  derived  from  two  molecules  of 
hexose  with  loss  of  one  molecule  of  water. 

2  CeH^Oe  —  H2O  =  Ci2H22On. 

The  disaccharides  can  be  hydrolyzed  under  the  influence 
of  acids  or  enzymes,  when  they  take  up  water  and  sepa- 


ORGANIC  CHEMISTRY  97 

rate  into  two  molecules  of  hexose, 

Cl2ll22Oii    -f-    H^O    =    2   CeHl^Oe 

The  reverse  process,  the  building  up  of  the  disaccharides 
from  the  monosaccharides  has  so  far  never  been 
accomplished  in  a  practical  way. 

There  are  three  disaccharides,  sucrose  (cane  sugar), 
maltose  (malt  sugar),  and  lactose  (milk  sugar).  One 
molecule  of  sucrose  on  hydrolysis  gives  one  molecule  of 
glucose  and  one  molecule  of  fructose,  the  mixture  of  the 
two  being  known  as  invert  sugar.  From  a  molecule 
of  maltose  on  hydrolysis  we  obtain  two  molecules  of 
glucose,  while  lactose  gives  one  molecule  of  glucose  and 
one  molecule  of  galactose. 

A  polysaccharide  is  formed  from  an  indefinite  number 
of  molecules  of  hexose  combined  together  with  loss  of 
water.  Since  it  is  impossible  to  ascertain  the  exact 
number  of  monosaccharide  molecules  united  together 
it  is  customary  to  write  the  formulae  of  the  polysac- 
charides  thus  (CsH.ioOs)x,  x  representing  an  unknown 
number.  On  hydrolysis  the  polysaccharides  are  broken 
down  in  successive  steps,  passing  through  various  stages 
of  complexity  until  the  monosaccharide  is  left.  The 
most  valuable  of  the  polysaccharides  is  starch,  the  cheap- 
est and  most  plentiful  of  our  food-stuffs.  When  hydro- 
lyzed  by  acids  or  by  the  amylolytic  enzymes  starch 
gives  first  a  series  of  dextrins  (polysaccharides  of  smaller 
molecular  weight),  then  the  disaccharide  maltose,  and 
finally  glucose.  It  is  in  this  way  that  the  commercial 
glucose  used  as  sweetening  for  cheap  confectionery  is 
made. 

For  the  most  part  the  reactions  of  the  carbohydrates 
are  those  of  the  ketones  and  aldehydes.  In  the  case 
of  certain  of  the  di-  and  polysaccharides  however  the 
aldehydic  and  ketonic  groupings  have  been  destroyed 


98  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

in  the  union  of  the  molecules,  and  the  characteristic 
reactions  of  these  groups  can  only  be  observed  after 
the  complex  molecule  has  been  hydrolyzed  to  the  mono- 
saccharides.  This  is  true  of  the  polysaccharides  starch, 
dextrin,  and  glycogen,  and  also  of  the  very  important 
disaccharide  sucrose  (cane  sugar). 

The  most  important  reaction  of  the  sugars  is  their 
reducing  action  on  the  metallic  oxides.  A  solution 
known  as  Fehling  solution,  which  contains  cupric  ions, 
has  long  been  used  as  a  test  for  sugars  in  physiological 
fluids.  Various  modifications  and  improvements  of 
this  reagent  have  been  devised  but  the  general  principal 
remains  the  same.  The  cupric  ion  imparts  to  the  solu- 
tion a  blue  color;  on  heating  in  the  presence  of  a  reducing 
sugar  this  color  changes,  passing  through  shades  of 
green  and  yellow  to  red,  owing  to  the  reduction  of 
cupric  to  cuprous  ions,  and  finally  a  dark  red  precipitate 
of  cuprous  oxide,  Cu20,  settles  out.  This  reaction, 
being  very  simple  and  accurate,  is  commonly  used  in 
testing  for  sugar  in  the  urine.  As  it  depends  on  the 
presence  of  the  carbonyl  group  of  the  aldehydes  or 
ketones,  cane  sugar  and  the  polysaccharides  will  not 
react.  For  the  most  part  any  reducing  sugar  present 
in  the  urine  is  assumed  to  be  dextrose,  as  this  is  the  only 
sugar  commonly  present  or  of  great  physiological  signifi- 
cance. When  necessary  specific  tests  can  be  used  for 
further  differentiation.  By  using  a  carefully  prepared 
solution  in  which  the  quantities  of  reagent  present 
are  accurately  known  the  estimation  of  reducing  sugar 
by  Fehling  solution  may  be  made  quantitative  instead 
of  merely  qualitative. 

The  carbohydrates  are  frequently  classified  according 
as  they  are  or  are  not  fermentable  with  yeast.  Fer- 
mentation is  a  term  used  for  decomposition  brought 
about  by  the  lower  organisms  through  the  enzymes 


ORGANIC  CHEMISTRY  99 

which  they  contain.  The  distinction  between  fermen- 
tation and  other  enzyme  actions  which  involve  decom- 
position of  the  substance  acted  on,  rests  on  the  fact 
that  fermentation  is  a  simple  breaking  up  of  the  fer- 
menting molecule  itself  into  smaller  molecules,  whereas 
in  other  decompositions  this  breaking  up  is  accompanied 
by  combination  with  other  atoms  or  groups  to  form 
the  new  molecules.  This  distinction  will  be  clearer 
on  comparing  two  typical  reactions  of  each  kind.  The 
fermentation  of  dextrose  to  produce  alcohol  is  represented 
by  the  following  equation 

C6H1206=  2C2H5OH  +  2C02, 

while  hydrolytic  decomposition  of  a  disaccharide  to  a 
monosaccharide  is  accompanied  by  the  addition  of  a 
molecule  of  water. 

Ci2H220n  +  H20  =  2C6Hi206. 

Owing  to  the  presence  of  fermentative  bacteria  in  the 
intestines  digestion  is  apt  to  be  accompanied  by  more 
or  less  fermentation,  the  amount  depending  partly  on 
the  numbers  of  these  bacteria  present  and  partly  upon 
the  kind  of  food  eaten.  This  fermentation  leads  to  the 
production  of  irritating  acids  and  gases  and  may  cause 
extreme  discomfort  when  allowed  to  become  excessive. 

The  most  important  fermentation  from  a  practical 
view  point  is  the  alcoholic  fermentation  of  dextrose 
just  referred  to.  To  bring  about  this  fermentation 
yeast  is  allowed  to  grow  in  a  solution  of  the  sugar.  The 
yeast  contains  an  enzyme  zymase,  which  ferments  the 
sugar,  the  energy  set  free  in  the  reaction  being  utilized 
by  the  yeast  plant  in  its  growth.  It  used  to  be  supposed 
that  this  fermentation  was  part  of  the  vital  process  of 
the  plant  and  therefore  could  not  be  carried  on  except 
through  the  agency  of  the  living  cell,  but  Buchner  in 


100  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

1897  succeeded  in  fermenting  sugar  by  a  yeast  extract 
which  had  been  so  treated  that  it  was  impossible  that  a 
single  living  cell  could  have  existed  in  it. 

Zymase  acts  only  on  monosaccharides,  but  yeast 
contains  another  enzyme,  invertase,  which  hydrolizes 
cane  sugar  to  dextrose  and  fructose,  thus  preparing  it 
for  the  action  of  the  zymase,  so  that  cane  sugar  solution 
makes  a  good  medium  for  fermentation.  Starch  cannot 
be  fermented  by  yeast,  but  the  diastatic  enzymes  present 
in  plant  cells  and  in  the  digestive  juices  break  it  down  into 
maltose,  which  is  acted  upon  by  maltase,  another  enzyme 
in  the  yeast  cell,  and  hydrolized  to  dextrose,  which 
is  then  fermented  by  the  zymase.  Starch  can  therefore 
be  used  as  a  source  of  alcohol  by  allowing  these  different 
enzymes  to  act  upon  it  in  turn.  It  is  in  this  way  that 
most  of  the  alcohol  of  commerce  is  prepared,  both  for 
use  as  a  beverage  and  for  industrial  purposes. 


CHAPTER  XVII 

AROMATIC  COMPOUNDS 

The  aromatic  compounds  differ  from  the  aliphatic 
in  constitution  and  in  general  properties.  Originally 
the  term  was  applied  to  a  small  group  of  substances 
with  a  pleasant  aromatic  odor.  Later  many  other 
substances  were  added  on  the  ground  of  similarity  in 
chemical  properties  rather  than  odor,  until  now  the 
group  is  larger  than  that  of  aliphatic  compounds  and  the 
distinction  is  based  on  structure  only.  The  great  host 
of  coal-tar  products,  so-called  because  they  are  obtained 
from  the  tar  left  behind  on  the  distillation  of  coal, 
belong  for  the  most  part  to  the  aromatic  series.  Flavor- 
ing extracts,  perfumes,  dyes,  medicines,  and  some  of  our 
most  powerful  explosives  are  among  the  many  substances 
obtained  directly  or  indirectly  from  this  tar  which  is  a 
mine  of  wealth  to  the  manufacturing  chemist. 

The  aromatic  compounds  have  as  their  mother  sub- 
stance six  carbon  atoms  arranged  in  a  ring,  or,  as  it  is 

C 

...     ,  ,  c/\c 

usually  written   for   convenience,   a  hexagon,       I       I 

C\/C 

C 

Each  of  these  carbons  has  two  valences  used  up  by  its 
neighbors  on  either  side,  a  third  holds  a  monovalent 
atom  or  group,  and  the  fourth  is  supposed  to  be  directed 
toward  the  centre  of  the  ring,  where  the  six  meeting 
together  are  held  in  equilibrium  by  their  mutual  attrac- 

101 


102  Cfr£M/S3.'RY  FOR  NURSES  AND  STUDENTS 

c— 


— c 


tion, 


— C 


C— 


.     The  strength  of  this  attraction 


v 

c 


i 
is  such  that  this  carbon  ring  is  perfectly  stable,  behaving 

in  all  respects  like  a  saturated  compound  in  spite  of 
these  apparently  free  valences. 

The  simple  hydrocarbon,  C6H6,  with  each  carbon 
joined  to  one  hydrogen  atom,  is  called  benzene,  and  the 
aromatic  compounds  may  be  looked  upon  as  derived 
from  this  by  replacement  of  one  or  more  H's  by  other 
atoms  or  groups.  For  this  reason  the  six-carbon  ring 
is  spoken  of  as  the  benzene  ring  or  nucleus.  The  radicle 
C6H5,  corresponding  to  the  radicles  CH3,  C2H5,  etc. 
is  called  the  phenyl  radicle.  The  higher  hydrocarbons 
are  formed  by  substituting  alkyl  groups  for  hydrogen  in 
benzene,  as  for  instance  toluene,  C6H5.CH3;  xylene,  C6H4 
(CH3)2;  ethylbenzene,  C6H5.C2H5.  The  alkyl  groups  thus 
introduced  are  spoken  of  as  side  chains.  There  may  be 
one  or  more  side  chains  in  the  ring,  and  these  may  be 
of  any  length,  according  to  the  size  of  the  group  intro- 
duced, and  may  be  saturated  or  unsaturated.  Styrene, 
C6H5.CH:CH2,  is  an  aromatic  compound  with  an  un- 
saturated side-chain. 

It  would  be  far  beyond  the  scope  of  this  book  to  deal 
with  the  aromatic  compounds  in  detail.  A  few  general 
characteristics  will  be  pointed  out,  but  for  further  in- 
formation a  larger  work  must  be  consulted. 

Aromatic  compounds  exist  which  have  the  phenyl 
radicle  combined  with  halogen  to  give  halogen  derivatives, 
with  hydroxyl  to  give  alcohols,  with  carbonyl  to  form 


ORGANIC  CHEMISTRY  103 

ketones  and  aldehydes,  and  with  carboxyl  to  form  acids, 
and  these  groups  may  be  directly  attached  to  the  nucleus 
or  may  be  separated  from  it  by  a  longer  or  shorter  chain 
of  carbon  atoms.  While  the  properties  of  all  these 
characteristic  groups  are  somewhat  modified  by  the 
benzene  ring  to  which  they  are  attached,  they  resemble 
the  corresponding  aliphatic  compounds  sufficiently  in 
their  general  reactions  so  that  no  special  attention  need 
be  given  to  them  here.  It  may  be  taken  as  a  general 
rule  that  side-chains  and  their  substituent  groups 
behave  like  aliphatic  compounds,  whereas  the  nucleus 
and  any  substituent  introduced  into  the  nucleus  directly 
will  show  aromatic  properties.  This  is  particularly 
evident  in  the  case  of  compounds  containing  hydroxyl, 
so  much  so  that  compounds  with  hydroxyl  in  the  nucleus 
are  classed  together  under  the  name  of  phenols,  and  only 
those  with  the  hydroxyl  in  the  side-chain  of  an  aromatic 
nucleus  are  called  aromatic  alcohols.  The  phenols,  while 
showing  certain  alcoholic  characteristics,  are  so  in- 
fluenced by  the  presence  of  the  benzene  nucleus  that  they 
behave  like  weak  acids,  forming  salts  by  replacement  of 
the  H  of  the  OH  with  Na  or  K,  e.g.  C6H5ONa,  sodium 
phenolate.  On  account  of  this  acid  characteristic  the 
first  member  of  the  series,  phenol,  was  supposed,  when 
first  discovered,  to  be  an  acid,  and  was  named  carbolic 
acid,  a  name  which  is  still  retained  in  general  use  al- 
though chemically  incorrect.  The  phenols  in  general 
have  antiseptic  properties,  and  some  of  the  higher 
members,  as  well  as  carbolic  acid,  are  used  as  antiseptics, 
preservatives,  and  deodorants. 


CHAPTER  XVIII 
PROTEINS  AND  VITAMINES 

One  of  the  most  important,  and  one  of  the  most  com- 
plex, groups  of  substances  with  which  the  chemist  has 
to  deal  is  the  group  of  proteins. 

On  heating  any  animal  fluid  or  tissue  extract  an 
insoluble  substance  is  obtained  as  a  precipitate.  If 
this  precipitate  be  carefully  dried  and  analysed  it  will  be 
found  to  consist  of  one  or  more  members  of  a  well  defined 
group  of  substances  of  similar  chemical  and  physical 
properties  which  are  classed  together  as  proteins.  The 
proteins  all  contain  as  essential  constituents  C,  H,  0,  N, 
and  S,  are  all  built  up  on  the  same  chemical  principle, 
and  therefore  have  a  number  of  reactions  in  common. 
They  have  in  addition  certain  specific  characteristics 
which  make  it  possible  to  subdivide  them  into  smaller 
groups.  Their  molecules  are  so  complex  that  it  is 
impossible  to  assign  any  simple  formulae  to  them,  and 
the  only  information  we  can  obtain  as  to  their  structure 
comes  from  studying  the  root  substances  of  which  they 
are  built  up. 

Proteins,  like  the  polysaccharides,  can  be  hydrolyzed 
by  inorganic  acids,  alkalies,  or  suitable  enzymes.  Of 
these  methods  enzyme  action  is  the  most  advantageous, 
since  it  goes  on  at  ordinary  temperatures,  is  less  strenuous 
and  therefore  less  apt  to  lead  to  undesirable  decomposi- 
tion products,  and  is  easier  to  regulate  in  such  a  way  as 
to  permit  of  the  isolation  of  intermediate  products. 
Careful  work  has  shown  that  hydrolysis  takes  place  in 
steps,  giving  products  of  gradually  decreasing  complexity 

104 


ORGANIC  CHEMISTRY  105 

until  ultimately  we  obtain  a  mixture  of  simple  com- 
pounds, all  of  one  type,  known  as  amino  acids. 

The  amino  acids  are  derived  from  the  aliphatic  acids 
such  as  acetic  acid  by  the  introduction  of  various  sub- 
stituent  groups  into  the  molecule.  They  are  called 
amino  acids  from  the  fact  that  they  all  contain  the  amino 
group,  —  NH2,  attached  to  the  carbon  atom  nearest 
to  the  carboxyl  group.  The  simplest  amino  acid  is 

OTT  OOOTT  • 
glycine,  ^TT'  '  others  may  contain  longer  carbon 

,      .         (CH3)2.CH.CH2.CH.COOH; 
chains,    such    as  leuaine,  NH 

may  have  other  substituents  present,  as  tyrosine, 
OH.C6H4.CH2CH.COOH  with  ft  phenolic  group  in  the 

NH 

C6H4<(">CH 
molecule,  or  tryptophane,  Q— CH2— CH— COOH, 

NH2 

containing  what  is  known  as  the  indole  ring]  or  may 
have  more  than  one  amino  group  present,  as  arginine, 
HN:QNH.CHa.CH,CH,C|COOH.  Onehas  sulphur 

present,'^,   COOH.gH/CH.S.S.CH.CH.COOH. 

Many  of  these  acids  are  combined  together  in  varying 
proportions  to  form  one  protein  molecule,  the  separate 
amino  acids  having  somewhat  the  same  relationship  to 
the  protein  as  the  bricks  and  stones  of  which  a  building 
is  made  to  the  complete  edifice.  Just  as  an  almost  in- 
finite number  of  different  styles  of  architecture  can  be 
produced  from  a  few  simple  types  of  building  material  so 
proteins  are  found  in  the  most  diverse  shapes  and  forms. 
White  of  egg,  lean  meat,  the  curd  of  milk,  nuts  of  all  kinds, 
hair,  and  horn  are  all  types  of  protein  substances. 


106  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

The  importance  of  protein  as  food  substance  will  be 
discussed  later.  Here  it  is  sufficient  to  remark  that  the 
indispensable  element  which  the  proteins  supply  is  the 
nitrogen  atom  present  in  the  amino  group,  this  being 
apparently  the  only  form  in  which  nitrogen  is  assimilable 
to  any  extent  by  the  animal  organisms.  Plants  have  the 
power  of  synthesizing  protein  from  the  nitrogen  of  in- 
organic salts,  carbon  dioxide,  and  water,  but  animals 
lack  this  ability  and  are  therefore  dependent  on  what  they 
can  get  from  the  plants,  either  directly  or  through  the 
medium  of  other  herbivorous  animals. 

Vitamines. — It  has  been  found  that  a  diet  which  con- 
tains sufficient  fat,  carbohydrate,  protein,  and  mineral 
matter  may  still  be  insufficient  for  growth  or  even  for 
the  maintenance  of  the  body  in  a  healthy  condition. 
Sailors  on  long  voyages,  deprived  of  fresh  fruits  and  vege- 
tables, the  inhabitants  of  certain  parts  of  the  orient,  whose 
diet  consists  almost  entirely  of  polished  rice,  and  babies 
fed  exclusively  on  sterilized  milk,  are  all  subject  to 
certain  diseases  which  can  be  cured  either  by  introducing 
other  foods  into  the  dietary  or  by  the  administration  of 
small  quantities  of  substances  extracted  from  rice,  bran, 
yeast,  or  orange  and  lemon  juice.  Diseases  of  this 
nature,  of  which  scurvy  and  beri-beri  are  typical,  are 
called  deficiency  diseases,  and  to  the  curative  substances 
contained  in  fruits  and  vegetables  was  given  the  name 
vitamines.  Recently  this  name  has  been  extended  to 
include  certain  growth-promoting  substances  of  which 
some  are  found  in  fruits,  vegetables,  and  the  outer  coats 
of  cereals,  and  some  in  certain  fats,  especially  the  fat 
of  egg  yolk,  butter,  cod-liver  oil,  and  beef  suet.  Both 
the  chemical  nature  and  the  physiological  effect  of  the 
vitamines  are  still  somewhat  obscure,  but  their  importance 
in  the  diet  is  well  recognized. 


\ 


SECTION  III 
PHYSIOLOGICAL  CHEMISTRY 

CHAPTER  XIX 
DIGESTION 

In  order  to  maintain  a  living  animal  in  health  and 
activity  it  must  be  supplied  with  enough  material  to 
provide  for  the  repair  and  rebuilding  of  the  worn-out 
tissues,  for  the  energy  which  it  uses  up  in  its  various 
movements,  and  for  growth  in  the  case  of  the  young. 
All  this  must  come  from  the  food,  and  the  process  of 
digestion  consists  in  breaking  down  the  various  complex 
food  substances  into  simpler  soluble  forms  of  which. the 
organism  can  make  use,  a.nd  is  followed  by  the  selection 
and  absorption  of  the  useful  portions,  and  the  rejection 
and  excretion  of  the  useless  material.  The  assimilation 
of  the  food  is  the  process  of  building  up  these  simple  de- 
composition products  of  the  food  into  the  tissues  of  the 
body  and  the  stores  of  reserve  material  which  can  be  used 
to  supply  energy  as  needed.  The  whole  series  of  pro- 
cesses through  which  the  organism  goes  in  the  course  of 
its  vital  activities,  the  breaking  down  of  complex  pro- 
ducts into  simpler  ones  and  the  building  up  of  simple  into 
more  complex  substances,  is  called  metabolism.  Metab- 
olism includes  not  only  digestion  and  assimilation  but 
all  the  chemical  reactions  which  take  place  in  the  body 
of  a  living  animal. 

The  essential  food  for  any  animal  must  contain  fats, 
carbohydrates,  and  proteins  (these  three  being  grouped 

107 


108  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

together  as  the  organic  food-stuffs),  water,  various 
mineral  salts,  and  small  quantities  of  organic  acids 
which  are  beneficial  if  not  absolutely  essential,  along 
with  the  growth  promoting  substances  called  vitamin es. 
Most  substances  used  as  food  are  composed  of  a  mixture 
of  all  these  in  varying  proportions.  It  is  the  business 
of  the  dietician  to  determine  what  are  the  ideal  propor- 
tions in  order  to  obtain  the  best  results  and  what  food 
or  combination  of  foods  is  best  suited  to  the  human  sys- 
tem. Before  any  conclusions  can  be  reached  with  regard 
to  this  it  is  necessary  to  follow  the  course  of  the  food- 
stuffs through  digestion  and  assimilation  in  order  to 
determine  the  function  of  each  and  the  factors  which 
add  to  or  detract  from  its  efficiency. 

In  the  mouth  the  food  is  crushed  and  torn  apart  by 
the  teeth  into  small  particles,  not  only  in  order  to  facili- 
tate swallowing  but  also  to  expose  as  large  a  surface 
as  possible  to  the  digestive  juices  and  to  aid  in  solution 
(see  page  28).  It  is  also  mixed  with  the  saliva,  the 
first  of  these  dige.stive  juices  with  which  it  comes  in 
contact.  The  saliva  is  the  mixed  secretion  of  the  glands 
of  the  mouth,  of  which  the  largest  and  most  important 
are  the  parotid,  which  opens  into  the  cheek  just  opposite 
the  second  molar,  the  submaxillary,  which  opens  between 
the  two  halves  of  the  lower  jaw  bone,  and  the  subhngual, 
under  the  tongue,  just  behind  the  submaxillary.  The 
secretion  of  these  three  differs  somewhat,  the  parotid 
producing  a  thin  watery  fluid,  while  the  lower  glands 
give  a  thicker,  slimy  secretion  which  serves  to  lubricate 
the  food  particles  so  that  they  slip  down  the  throat  more 
easily. 

The  salivary  glands  secrete  more  or  less  continually, 
but  they  are  stimulated  to  greater  activity  by  various 
means,  mechanical  pressure  (holding  a  stone  in  the  mouth 
as  athletes  sometimes  do  to  prevent  their  mouths  and 


PHYSIOLOGICAL  CHEMISTRY  109 

throats  from  becoming  dry),  chemical  stimulus  (from 
the  soluble  substances  in  the  food),  and  by  the  psychic 
influences,  odor,  sight,  or  even  thought  of  appetising 
food:  while  on  the  other  hand  excitement,  fear,  anger, 
or  embarrassment  prevent  the  flow  of  saliva,  so  that  the 
mouth  and  throat  become  dry  and  parched  and  the 
swallowing  of  food  is  rendered  difficult. 

Besides  certain  inorganic  salts  of  which  the  exact 
function  is  unknown  the  saliva  contains  enzymes  and 
a  large  amount  of  water.  The  water  aids  in  the  swallow- 
ing of  food,  helps  to  dissolve  the  soluble  material,  and 
when  reabsorbed  through  the  intestinal  walls  carries 
the  dissolved  substances  with  it  into  circulation  through 
the  blood  stream,  from  which  they  can  be  taken  by  the 
various  tissues  as  required.  The  most  important  enzyme 
present  is  the  starch-hydrolysing  enzyme  pytalin,  or 
salivary  diastase  as  it  is  sometimes  called  from  its  close 
resemblance  to  diastase,  the  starch-hydrolysing  enzyme 
of  the  barley  grain.  There  are  also  small  amounts  of 
maltase,  which  converts  maltose  into  dextrose,  and  a 
proteolytic  enzyme,  but  these  are  relatively  unimportant. 

The  main  function  of  the  saliva  appears  to  be  the 
breaking  down  of  the  starch  of  the  food,  chiefly  into 
maltose  although  a  certain  amount  is  further  hydrolysed 
to  dextrose.  This  change  accounts  for  the  fact  that 
starchy  food  grows  slightly  sweeter  as  it  is  chewed.  It 
is  to  be  noted  that  while  saliva  acts  readily  on  cooked 
starch  its  action  on  raw  starch  is  very  slow,  a  fact  which 
shows  the  importance  of  thorough  cooking  of  all  starchy 
food  so  that  it  may  be  properly  digested.  Moreover 
thorough  chewing  in  the  mouth  is  of  even  greater  im- 
portance as  it  is  necessary  that  the  food  should  be  well 
saturated  with  saliva  in  order  that  the  action  may  be  as 
complete  as  possible.  Long  mastication  ensures  a 
copious  flow  of  saliva  as  well  as  effecting  a  more  complete 


110  €HEMISTRY  FOR  NURSES  AND  STUDENTS 

mixing  with  the  food.  It  is  a  curious  fact  that,  quite 
apart  from  the  action  on  carbohydrates,  all  food  digests 
faster  in  the  stomach  if  mixed  with  saliva. 

Although  the  action  of  the  saliva  in  the  mouth  itself 
is  only  superficial  it  continues  after  the  food  has  passed 
down  into  the  stomach,  during  the  long,  gradual  process 
of  mixing  with  the  stomach  juice.  When  that  mixing 
has  been  accomplished  salivary  digestion  is  stopped 
since  the  stomach  juice  is  too  strongly  acid  to  allow  the 
continued  activity  of  the  ptyalin. 

The  stomach  is  an  elastic  pocket,  large  at  one  end, 
small  at  the  other,  lying  between  the  esophagus  and 
the  intestines  and  serving  as  a  store-house  where  food 
can  be  retained  and  where  it  undergoes  a  certain  amount 
of  preliminary  digestion,  passing  into  the  intestines  in 
small  amounts  at  a  time  for  the  completion  of  the 
process.  The  smaller  end  is  called  the  pyloric  portion, 
from  the  pylorus  or  thick  ring  of  muscular  tissue  through 
which  it  passes  into  the  small  intestine,  while  the  larger 
end,  connecting  with  the  esophagus,  is  distinguished  as 
thefundus,  or  cardiac  portion.  The  lining  of  the  stomach 
is  a  soft  mucous  membrane,  somewhat  like  the  inside 
of  the  cheek  to  the  touch,  but  lying  in  folds.  All 
through  these  folds  are  small  glands  by  which  the  gastric 
juice  is  produced  and  poured  into  the  stomach. 

The  walls  of  the  stomach  being  perfectly  elastic,  are 
able  to  contract  and  expand  in  proportion  to  the  amount 
of  food  present.  In  the  absence  of  food  the  walls 
collapse  until  they  are  in  contact,  but  as  the  food  passes 
down  the  esophagus  the  fundus  becomes  gradually 
distended,  the  food  which  enters  first  lying  next  the 
wall  while  the  remainder  is  packed  in  the  centre  layer 
by  layer.  Properly  speaking,  therefore,  the  normal 
stomach  is  never  empty,  since  there  is  never  an  unfilled 
space.  There  is  a  certain  diseased  condition,  however, 


PHYSIOLOGICAL  CHEMISTRY  111 

in  which  the  stomach  remains  permanently  dilated  in 
the  absence  of  food,  a  condition  which  causes  much  dis- 
tress to  the  individual. 

The  stomach  glands,  like  the  salivary  glands,  may  be 
stimulated  by  various  influences.  Certain  chemicals, 
particularly  the  soluble  extractives  of  the  food,  cause 
the  immediate  production  of  juice.  The  extractives  of 
meat  are  most  effective,  hence  the  value  of  a  clear  soup 
as  an  appetizer.  More  effective  still  however  are  the 
psychic  influences,  pleasurable  anticipation  causing  a 
copious  flow  of  juice  while  anger  or  excitement  hinders 
or  even  prevents  it.  This  was  very  well  shown  by  the 
experiments  of  the  physiologist,  Pawlow,  who  operated 
on  dogs  in  such  a  way  as  to  produce  a  passage  into  the 
throat  and  the  stomach  through  which  food  could  enter 
or  leave  without  the  dog's  knowledge.  Through  the 
stomach  opening  he  could  observe  the  progress  of  diges- 
tion under  various  conditions.  He  found  that  the  flow 
of  gastric  juice  began  as  soon  as  a  plate  of  food  was  set 
before  the  dog  and  continued  while  he  ate,  whether  the 
food  passed  into  the  stomach  or  dropped  out  through 
the  esophageal  opening,  but  stopped  immediately  if  the 
dog  was  confronted  with  a  cat.  A  somewhat  similar 
observation  was  made  on  a  child  and  it  was  found  that 
when  he  was  teased  or  distressed  in  any  way  the  secretion 
of  his  stomach  glands  stopped.  In  another  experiment 
two  dogs  were  given  pieces  of  meat  of  equal  size,  but  one 
dog  was  allowed  to  eat  his  meat  in  the  ordinary  way, 
while  in  the  other  case  it  was  inserted  through  the 
stomach  opening  without  the  dog's  knowledge.  At  the 
end  of  an  hour  or  two  the  meat  in  the  stomach  of  the 
first  dog  was  found  to  be  much  better  digested  than  that 
in  the  stomach  of  the  second  where  no  psychic  influence 
came  into  play. 

Where  food  is  unappetising  it  is  not  entirely  undigested 


112  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

because  the  chemical  influences  will  still  have  some 
effect,  but  digestion  is  much  slower  owing  to  the  smaller 
supply  of  juice  from  the  glands.  It  is  highly  desirable 
therefore  that  food  should  be  not  only  nutritious,  but 
also  attractively  served,  eaten  slowly,  so  as  to  ensure 
thorough  mastication,  and,  as  far  as  can  be  secured,  amid 
pleasant  surroundings.  As  anger  and  emotion  inhibit 
the  action  of  the  glands  all  disagreeable  or  exciting  topics 
should  be  avoided  at  meal  time.  In  the  case  of  children 
it  has  been  found  that  even  vigorous  play  just  before  a 
meal  has  a  bad  effect  on  the  activity  of  the  stomach 
glands  and  should  therefore  be  prevented.  While  all 
these  have  been  long  recognized  more  or  less  as  good 
general  rules  of  conduct  it  was  only  by  actual  experiment 
that  they  could  be  shown  to  be  based  on  sound  physiologi- 
cal reasons. 

Pure  gastric  juice  is  a  colorless  liquid  looking  much 
like  water,  with  a  slightly  sour  taste  due  to  a  little 
hydrochloric  acid  which  is  always  present  to  the  extent 
of  about  0.2-0.4  per  cent,  in  the  gastric  juice  of  a  normal 
individual.  In  much  larger  amounts  than  this  it 
interferes  with  digestion,  and  the  condition  is  said  to  be 
one  of  hyperacidity.  Hypoacidity  on  the  other  hand  is 
the  condition  where  there  is  too  little  acid  in  the  gastric 
juice,  and  is  equally  injurious.  The  principal  enzyme 
present  is  pepsin,  which  acts  upon  proteins,  bringing 
about  the  first  step  in  their  decomposition  and  producing 
certain  slightly  less  complex,  soluble  products  known  as 
peptones  and  proteases.  Pepsin  as  secreted  by  the  glands 
is  in  the  inactive  zymogen  state  (see  page  51),  and  only 
becomes  active  in  the  presence  of  hydrochloric  acid,  so 
that  the  activating  of  this  enzyme  is  one,  although  prob- 
ably not  the  only,  function  of  the  acid  in  the  stomach. 
Besides  pepsin  we  find  two  other  enzymes  present, 
lipase,  or  fat  splitting  enzyme,  and  rennin}  an  enzyme 


PHYSIOLOGICAL  CHEMISTRY  113 

which  coagulates  milk  into  a  smooth  curd.  Thanks  to 
the  lipase  present  gastric  juice  has  considerable  fat- 
digesting  power,  provided  the  fat  is  sufficiently  finely 
divided.  From  50-80  per  cent,  of  the  fats  in  milk  and 
egg  yolk,  where  they  are  present  as  an  emulsion,  are 
hydrolyzed  to  fatty  acids  and  glycerine  in  the  stomach, 
while  98-99.5  per  cent,  of  fats  such  as  those  of  meats  and 
butter,  which  are  not  emulsified,  pass  unchanged  into 
the  intestines. 

Various  commercial  preparations  of  rennin  (or  rennet, 
as  it  is  sometimes  called)  extracted  from  the  stomachs 
of  calves  are  on  the  market  and  are  used  for  coagulating 
slightly  sweetened  and  flavored  milk.  The  curd  thus 
produced  is  called  junket  and  is  a  palatable  and  nutri- 
tious food.  It  seems  probable  that  this  coagulating 
or  clotting  of  the  milk  is  due  to  a  partial  hydrolysis 
of  the  casein  (the  protein  constituent  of  the  milk) 
into  a  simpler  and  less  soluble  form  to  which  the  name 
paracasein  has  been  given.  It  is,  then,  a  preliminary 
digestion  analogous  to  that  brought  about  by  pepsin 
when  proteins  are  hydrolysed  to  peptones  and  proteoses. 

In  the  normal  stomach  the  contents  of  the  pyloric 
region  are  continually  being  churned  up  by  the  periodic 
contraction  of  the  stomach  wall  with  a  kind  of  wave 
motion,  starting  at  the  slight  constriction  between 
fundus  and  pylorus  and  running  towards  the  pylorus. 
This  motion  at  first  very  slight,  becomes  mere  vigorous 
as  digestion  proceeds  and  the  contents  of  the  pyloric 
region,  under  the  combined  effect  of  churning  and  enzyme 
action  and  the  solvent  power  of  the  juice,  becomes  trans- 
formed into  a  semi-fluid  mass  called  chyme.  Finally, 
when  the  glands  have  secreted  enough  juice  to  give  a 
distinct  acid  reaction  to  the  chyme,  the  pylorus  relaxes 
and  the  next  wave  of  contraction  forces  a  portion  of  the 
chyme  through  into  the  intestine.  The  pylorus  then 


114  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

closes,  a  portion  of  the  food  mass  in  the  fundus  is  pressed 
toward  the  pylorus  and  digestion  continues.  The  length 
of  time  required  to  completely  empty  the  stomach 
varies  from  one  to  seven  hours  according  to  the  quantity 
and  character  of  the  food  eaten.  Protein  remains  longer 
in  the  stomach  than  carbohydrate,  fat  longer  than  pro- 
tein, and  mixtures  of  fat  and  protein  longer  than  either 
alone. 

In  considering  the  digestibility  of  a  food  a  distinction 
should  be  made  between  the  ease  of  digestion,  that  is  the 
rapidity  with  which  the  food  leaves  the  stomach,  and 
completeness  of  digestion.  In  general  the  more  fluid 
the  food  the  more  quickly  will  it  pass  through  the 
stomach,  but  it  does  not  necessarily  follow  that  it  is 
more  digestible,  in  the  sense  of  providing  more  nutri- 
ment, than  a  food  which  remains  in  the  stomach  longer. 
Fluid  white  of  egg  is  more  quickly  digested,  and  hence 
is  usually  considered  more  digestible,  but  more  nutri- 
ment is  obtained  from  hard-boiled  egg  white.  In  cases 
of  weak  digestion  it  is  often  desirable  to  sacrifice  com- 
pleteness for  ease  of  digestion,  although  where  the  diges- 
tion is  good  it  is  more  economical  to  give  those  foods 
which  are  digested  as  completely  as  possible. 

Some,  but  probably  a  very  small  proportion,  of  the 
food  is  directly  absorbed  into  the  system  through  the 
stomach  walls.  Water  is  so  absorbed,  as  are  also  certain 
drugs  and  poisons,  as  is  shown  by  the  rapidity  with  which 
they  act  on  the  system.  Alcohol  is  directly  absorbed 
and  permeates  the  whole  system  with  great  rapidity, 
showing  its  effects  within  a  very  few  minutes  after  being 
swallowed.  The  bulk  of  the  food,  however,  reaches 
the  intestines,  where  it  undergoes  further  digestion  and 
is  finally  absorbed  through  the  intestinal  wall. 

The  small  intestine  is  a  tube  about  thirty  feet  long 
coiled  in  the  interior  of  the  body  cavity.  The  intestinal 


PHYSIOLOGICAL  CHEMISTRY  115 

juice  is  the  combined  secretion  of  the  intestinal  glands, 
a  large  number  of  small  glands  which  are  contained  in 
the  intestinal  wall,  the  pancreas,  a  very  large  gland 
opening  into  the  intestine  four  or  five  inches  below  the 
pylorus,  and  the  liver. 

The  pancreas,  like  the  other  digestive  glands,  produces 
its  secretion  only  in  response  to  definite  stimulus.  When 
the  acid  chyme  arrives  in  the  intestine  it  causes  the 
production  in  the  intestinal  wall  of  a  substance  called 
secretin,  which  acts  upon  the  pancreas  in  such  a  way  as  to 
bring  about  secretion  of  the  pancreatic  juice.  This  juice 
and  that  of  the  smaller  intestinal  glands  is  strongly 
alkaline  due  to  the  presence  of  carbonates.  This  alkali 
serves  to  neutralize  the  acid  of  the  chyme,  and  also  reacts 
with  the  fatty  acids  produced  by  the  hydrolysis  of  the 
fats,  forming  soaps  (see  page  91)  which  help  to  emulsify 
the  still  undecomposed  fats  and  render  them  more  suscep- 
tible to  the  attack  of  the  lipolytic  enzyme. 

There  are  several  enzymes  present  in  the  pancreatic 
juice,  of  which  the  most  important  are  steapsin, which 
hydrolyses  fats  to  glycerine  and  fatty  acids,  amylopsin, 
which,  like  ptyalin,  converts  starch  into  maltose  and 
therefore  supplements  the  action  of  the  saliva,  and  trypsin 
which  acts  on  proteins,  converting  them  into  amino 
acids.  Besides  these  there  are  also  lactase,  which 
hydrolyses  lactose  into  dextrose  and  galactose,  maltase, 
which  hydrolyses  maltose  into  dextrose  and  at  least 
occasionally  invertin  which  hydrolyses  cane  sugar  into 
dextrose  and  fructose. 

The  secretion  of  the  small  intestinal  glands  is  very  like 
that  of  the  pancreas  in  some  respects.  It  contains 
invertin,  maltase,  and  lactase,  and  in  addition  an  enzyme, 
erepsin,  which  acts  on  the  peptones  and  proteoses  produced 
by  the  pepsin  in  the  stomach,  completing  their  digestion 
into  amino  acids;  and  still  another  enzyme  enterokinase, 


116  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

which  serves  to  activate  the  trypsin,  possibly  in  some- 
what the  same  way  in  which  pepsin  is  activated  by  the 
hydrochloric  acid  of  the  gastric  juice.  If  collected 
alone,  as  directly  secreted  by  the  gland,  pancreatic 
juice  has  little  or  no  action  on  proteins,  but  when  mixed 
with  the  juice  from  the  intestinal  glands  it  acts  vigorously. 
On  the  other  hand,  the  juice  from  the  intestinal  glands 
alone  has  very  weak  digestive  action,  but  seems  to  serve 
mainly  to  strengthen  the  action  of  the  pancreatic  juice. 

The  liver  differs  from  the  other  digestive  glands  in 
producing  a  more  or  less  continual  secretion  which  is 
stored  up  in  the  gall-bladder  and  is  poured  from  this 
into  the  intestine  during  digestion.  This  secretion, 
known  as  the  bile,  is  a  thick,  viscous  fluid,  golden  or 
greenish  yellow  in  color.  When  for  any  reason  the  bile 
duct  becomes  stopped  up  the  disorder  known  as  jaundice 
follows,  and  the  coloring  matter  of  the  bile  becomes  dis- 
tributed through  the  body,  giving  a  yellowish  tinge  to 
the  skin.  Gall-stones  are  deposits  of  solid  matter  which 
for  some  reason  have  separated  out  from  the  bile  in  the 
gall-bladder,  .where  they  sometimes  cause  great  suffer- 
ing. While  the  bile  in  itself  has  little  or  no  digestive 
action,  it  has  a  remarkable  effect  in  assisting  the  action 
of  the  other  secretions,  especially  in  facilitating  the 
digestion  and  absorption  of  fats.  Not  only  has  it  great 
emulsifying  powers,  being  even  more  effective  than  the 
soaps  in  this  respect,  but  it  seems  to  be  able  to  enter  into 
some  peculiar  chemical  or  physical  combination  with  the 
fatty  acids  or  their  salts,  in  which  form  they  readily 
pass  through  the  intestinal  walls  into  the  lymph  vessels, 
from  which  they  are  carried  through  the  system.  In 
the  absence  of  bile  very  little,  if  any,  absorption  of  fat 
takes  place. 

After  the  chyme  has  passed  out  of  the  stomach  it  lies 
for  some  time  in  the  upper  loop  of  the  intestine,  while  the 


PHYSIOLOGICAL  CHEMISTRY  117 

intestinal  juices  are  poured  over  it  and  the  work  of 
digestion  continues.  After  a  time  a  churning  motion  of 
the  intestine  begins,  somewhat  like  the  contractions  of 
the  stomach,  and  the  food  is  divided  into  small  portions 
and  vigorously  churned.  This  motion,  besides  mixing 
the  food  with  the  digestive  juice  forces  it  into  closer 
contact  with  the  intestinal  wall  and  hence  increases  the 
absorption  from  the  intestine.  This  motion  continues 
for  some  time  and  then  stops,  to  be  succeeded  by  a 
slower  wave  motion  which  travels  down  the  intestine 
pushing  the  food  down  to  the  lower  end.  This  motion 
is  called  peristalsis,  and  is  of  great  importance.  Where 
the  tone  of  the  intestinal  wall  is  poor  and  peristalsis  is 
weak  constipation  results.  Certain  drugs,  such  as 
calomel  have  the  power  of  restoring  the  lost  tone  and 
stimulating  peristalsis  and  this  appears  to  be  a  function 
of  the  bile  also.  Mechanical  stimulus  seems  likewise 
effective,  hence  the  value  of  a  certain  amount  of  coarse, 
undigestible  material  such  as  the  cellulose  of  vegetables 
or  the  bran  of  cereals  in  the  diet.  These  substances  are 
insoluble  and  impervious  to  the  digestive  juice  of  human 
beings,  but  the  pressure  which  they  exert  on  the  walls  as 
they  pass  through  the  intestinal  tract  is  stimulating, 
peristalsis  is  increased,  and  hence  a  tendency  toward  con- 
stipation may  be  overcome. 

As  the  food  moves  down  the  digestive  tract  it  meets  no 
new  secretions,  but  the  juice  with  which  it  is  already 
saturated  continues  its  action  and  absorption  takes  place 
gradually.  From  the  small  intestine  it  passes  into  the 
large  intestine,  or  colon,  where  it  may  remain  a  day  or 
even  longer  before  being  excreted  from  the  body.  Ab- 
sorption continues  in  the  upper  part  of  the  colon,  but 
decreases  very  considerably  until  in  the  lower  part  there 
is  none  at  all.  There  are  no  secreting  glands  in  the  colon 
and  hence  no  digestive  juice  except  such  as  the  food 


118  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

brings  with  it,  but  there  are  large  numbers  of  bacteria 
which  act  on  the  food  producing  various  more  or  less 
injurious  decomposition  products. 

There  are  three  main  types  of  bacteria  which  inhabit 
the  human  digestive  tract,  the  putrefactive  bacteria, 
the  acid  forming  bacteria,  and  bacteria  of  the  class  known 
as  the  B.  Coli  type.  Of  these  the  putrefactive  bacteria 
seem  to  be  the  only  forms  which  are  very  actively  injuri- 
ous. They  produce  poisonous  decomposition  products 
which  are  absorbed  and  penetrate  the  system  causing 
many  more  or  less  marked  symptoms  ranging  from  mental 
depression,  drowsiness,  and  irritability,  generally  ac- 
companied by  physical  discomfort,  headache,  outbreak 
of  pimples,  cold  sores,  boils,  development  of  colds  or 
aggrevation  of  mild  chronic  ailments,  up  to  the  acute 
condition  recognized  as  ptomaine  poisoning.  The  longer 
the  food  residue  remains  in  the  colon  the  greater  the 
opportunity  for  its  decomposition  by  the  putrefactive 
bacteria,  hence  one  of  the  great  evils  of  constipation. 
Much  interest  was  aroused  a  few  years  ago  by  the  theory 
of  a  Russian  physiologist,  Metchnikoff,  who  regarded 
old  age  with  its  failing  powers  and  decreased  resistance 
as  the  result  of  gradual  poisoning  of  the  whole  system  by 
these  products  of  putrefaction  and  suggested  that  the 
secret  of  long  life  and  health  lay  in  eliminating  the  in- 
jurious organisms.  As  it  is  of  course  impossible  to 
sterilize  the  digestive  tract  of  an  animal  or  even  to 
render  it  less  favorable  for  the  bacterial  growth  the  only 
possible  method  of  disposing  of  the  putrefactive  bacteria 
is  by  taking  advantage  of  the  fact  that  when  two  races 
of  bacteria  are  growing  in  a  limited  space  the  stronger  and 
more  vigorous  will  gradually  crowd  out  the  weaker, 
until  finally  the  latter  disappears  altgoether.  Metchni- 
koff  therefore  sought  for  some  type  of  bacteria  which 
would  be  antagonistic  to  the  putrefactive  bacteria 


PHYSIOLOGICAL  CHEMISTRY  119 

and  which  could  be  cultivated  in  the  intestines  without 
themselves  producing  injurious  effects,  and  he  believed 
he  had  found  this  in  the  lactic  acid  bacteria  present  in 
sour  milk.  Accordingly  he  recommended  the  drinking 
of  sour  milk  or  buttermilk  containing  large  numbers  of 
lactic  acid  bacteria,  especially  those  of  a  certain  strain,  B. 
Bulgaricus,  which  could  be  developed  by  inocculating 
sterilized  milk  with  the  culture  and  keeping  it  for  a  few 
hours  in  a  warm  place.  The  buttermilk  cure  became 
the  fad  of  the  moment,  but  died  out  after  a  time  as  all 
dietetic  fads  are  sure  to  do.  Whether  buttermilk  is  or 
is  not  a  preventive  of  old  age  it  is  unquestionably  a 
wholesome  and  nutritious  drink  and  its  extensive  use 
might  well  be  encouraged,  but  perhaps  an  easier  and  surer 
method  of  reducing  intestinal  putrefaction  is  by  careful 
diet,  especially  by  limiting  the  amount  of  meat  eaten 
and  by  very  thorough  mastication  so  that  the  least  pos- 
sible amount  of  undigested  protein  reaches  the  region 
of  bacterial  activity.  An  increase  in  the  proportion  of 
carbohydrate  food  also  tends  to  decrease  putrefaction, 
partly  because  the  bacteria  will  not  attack  the  protein 
in  presence  of  sufficient  excess  of  carbohydrate,  and 
partly  perhaps  because  the  carbohydrates  in  their 
fermentation  produce  acid  which  is  unfavorable  to  the 
growth  of  many  forms  of  bacteria. 

While  bacteria  nourish  in  the  colon  and  the  lower  part 
of  the  small  intestine  they  are  not  found  in  the  upper 
part  of  the  intestine  nor  in  the  stomach;  in  fact  bacteria 
introduced  through  the  mouth  are  usually  destroyed  by 
the  acid  gastric  juice,  which  has  a  strong  antiseptic  effect. 

Summary. — The  three  digestive  juices  are  the  saliva 
of  the  mouth,  the  gastric  juice  of  the  stomach,  and  the 
intestinal  juice,  which  includes  the  secretion  of  the  small 
intestinal  glands,  the  pancreatic  juice,  and  the  bile. 
The  combined  effect  of  all  these  agents  is  to  decompose 


120  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

the  complex  and  insoluble  food  materials  into  simple 
molecules  which  are  soluble  and  which  can  be  absorbed 
and  either  decomposed  further  to  supply  energy  or 
built  up  into  body  substance  by  the  various  organs. 
Carbohydrates,  except  the  indigestible  cellulose,  are 
hydrolysed  to  monosaccharides,  the  action  taking  place 
chiefly  in  the  stomach  but  being  completed  in  the 
intestines.  Fats,  if  very  finely  divided,  are  hydrolysed 
in  the  stomach,  but  for  the  most  part  they  pass  into  the 
intestine  where  they  undergo  decomposition  into  fatty 
acids  and  glycerine.  Protein  undergoes  a  partial  decom- 
position in  the  stomach  and  the  products  of  this  action, 
as  well  as  any  protein  which  has  passed  through  the 
stomach  unchanged,  are  hydrolysed  to  the  amino  acids 
in  the  intestines.  The  mixture  of  food  and  digestion 
products  is  pushed  slowly  down  through  the  intestines 
while  absorption  takes  place  gradually.  In  the  lower 
end  of  the  small  intestine  and  the  colon  the  mass  is 
subjected  to  the  action  of  various  bacteria,  of  which  at 
least  one  race,  the  putrefactive  bacteria,  produce  in- 
jurious substances  which  are  absorbed  and  spread 
through  the  system. 


CHAPTER  XX 

ASSIMILATION 

Fats. — In  the  course  of  their  passage  through  the 
intestinal  wall  the  fatty  acids  and  glycerine  become 
recombined  into  fats  again,  although  the  character  of  the 
fat  is  usually  altered  somewhat,  fats  of  all  kinds  taken 
in  the  food,  vegetable  fats  and  oil,  butter,  pork  fat,  beef 
fat,  being  all  alike  converted  into  the  peculiar  body  fat 
of  the  animal  concerned.  This  fat  is  taken  up  from  the 
intestinal  wall  by  the  lymph  vessels  and  poured  directly 
into  the  blood,  by  which  it  is  transported  to  the  tissues, 
where  the  greater  part  of  it  is  deposited  as  reserve  mater- 
ial, though  a  certain  amount  may  be  combined  into  cell 
substance  or  burned  directly  if  needed  for  energy. 
Fat  is  a  very  convenient  form  in  which  to  lay  up  reserve 
food,  since  it  can  be  deposited  fairly  uniformly  over  the 
body,  causing  no  inconvenience,  except  when  present 
in  excessive  amounts,  and  can  be  readily  reconverted 
into  a  soluble  or  diffusible  form  for  rapid  transport  to 
any  part  of  the  body  where  it  may  be  needed  at  any 
time.  It  is  the  most  economical  fuel  available  to  the 
body,  giving  about  twice  as  much  heat  per  unit  weight 
as  either  carbohydrate  or  protein.  Moreover  it  is 
valuable  as  a  covering  and  protection  for  the  nerve 
endings  and  for  certain  other  delicate  organs.  In  order 
that  the  fat  reserve  may  be  very  quickly  available  for  the 
organism  fatty  tissue  is  permeated  with  a  network  of 
minute  blood  vessels,  and  if  there  is  too  great  an  extent  of 
such  tissue  the  effort  of  pumping  blood  through  all  these 
small  vessels  may  put  an  undue  strain  on  the  heart. 

121 


122  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

Where  there  is  a  tendency  toward  excessive  storage  of 
fat  in  the  tissues  it  should  be  guarded  against  by  careful 
dieting,  both  as  to  kind  and  amount  of  food  taken,  and 
by  excercise,  which  necessitates  the  burning  of  more  fat 
to  supply  the  energy.  Where  ordinary  care  in  this 
respect  is  insufficient  to  counteract  this  tendency  the 
advice  of  a  competent  physician  should  be  sought, 
as  incalculable  harm  may  be  done  by  some  of  the  drastic 
methods  of  "cure"  by  starvation  or  drugs  used  at 
random. 

Proteins. — The  amino  acids  produced  from  the  pro- 
teins by  digestion  are  absorbed  into  the  blood  stream  and 
carried  to  the  tissues.  From  these  amino  acids  the  body 
protein  is  built  up,  the  cells  being  the  builders  as  well  as 
the  firemen  who  prepare  the  fuel  and  keep  up  the  fires 
which  supply  the  necessary  energy  for  the  vital  activities. 
They  must  also  aid  in  the  destruction  of  unnecessary 
material  which  would  clog  up  the  system  and  have  an 
injurious  effect  if  allowed  to  accumulate.  In  the  young 
growing  organism  they  must  construct  new  tissue  to 
add  to  the  body  structure,  but  in  the  adult  it  is  only 
necessary  to  repair  the  waste  and  maintain  the  efficiency 
of  the  living  machine.  Their  task  is  complicated  by  the 
fact  that  they  have  only  second-hand  materials  with 
which  to  work  and  that  the  supply  of  those  is  too  often 
regulated  by  the  uncontrolled  appetite  of  the  body  they 
serve,  with  little  or  no  reference  to  the  actual  needs  of  the 
system.  In  such  a  case  the  cells  must  make  what  shift 
they  can,  destroying  or  excreting  the  surplus  thrust 
upon  them,  sifting  out  the  necessary  amino  acids  from 
the  rubbish,  and  if  necessary  tearing  down  and  burning 
the  body  substance  itself  in  order  to  maintain  the  life- 
giving  fires. 

Not  all  the  amino  acids  are  of  equal  importance; 
some  can  be  made  in  the  body  from  other  materials, 


PHYSIOLOGICAL  CHEMISTRY  123 

others  are  required  only  in  small  amounts,  while  still 
others  are  essential  for  growth  or  maintenance  of  life. 
An  animal  fed  on  maize  as  its  sole  protein  food  never 
attains  more  than  two  thirds  of  its  normal  growth, 
however  abudant  its  food  may  be  in  all  other  respects, 
but  if  a  small  amount  of  milk  be  added  to  the  diet  normal 
growth  is  induced.  Similar  results  are  obtained  with 
wheat  and  oats,  but  in  the  latter  case  gelatine  proved  a 
better  supplmentary  food  than  milk.  The  explanation 
is  believed  to  be  that  while  these  proteins  may  contain 
all  the  necessary  ami  no  acids  certain  ones  are  present 
in  very  small  quantity,  while  others  are  in  excess.  If 
some  other  protein  can  be  found  which  is  rich  in  the 
acids  which  the  first  lacks  and  poor  in  those  which  the 
first  contains  in  abundance  the  combination  of  the  two 
in  reasonable  amounts  will  be  more  satisfactory  as  a  food 
than  either  alone.  When  our  foods  have  been  more 
thoroughly  studied  from  this  point  of  view  we  -  will 
doubtless  be  able  to  arrange  various  combinations  of 
proteins  which  contain  the  correct  proportions  of  all 
the  amino  acids,  but  in  our  present  state  of  ignorance 
it  seems  to  be  the  safest  plan  to  include  in  the  diet  a 
variety  of  proteins  in  rather  small  amounts,  rather 
than  a  large  amount  of  any  one,  in  order  to  obtain  a  good 
average  of  amino  acids. 

Lack  of  the  fundamental  amino  acids  is  of  course  fatal 
for  the  building  cells,  since  no  other  food  material  con- 
tains nitrogen  and  hence  nothing  else  can  be  substituted 
for  protein.  On  the  other  hand  too  much  protein  causes 
a  great  deal  of  unnecessary  work  in  the  disposal  of  it. 
Unlike  carbohydrate  and  fat  protein  cannot  be  stored 
up  to  any  extent  as  reserve  material  in  the  body.  During 
active  growth  and  occasionally  after  a  long  wasting 
illness  or  a  hemorrhage  which  has  very  greatly  reduced 
the  amount  of  protein  in  the  body,  a  considerable  amount 


124  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

may  be  retained  in  the  tissues,  but  ordinarily  no  matter 
how  much  may  be  taken  in  it  is  practically  all  got  rid  of 
in  the  course  of  twenty-four  hours.  What  becomes  of 
this  protein  which  passes  through  the  system?  The 
amino  acids  which  are  not  needed  in  that  form  first 
undergo  deaminization  in  the  tissues,  that  is,  the  nitrogen- 
containing  part  of  the  molecule  is  split  off  from  the  rest 
and  excreted  promptly  in  the  urine,  while  the  remainder 
may  be  converted  into  carbohydrate  or  fat  and  either 
stored  in  the  body  or  burned  to  carbon  dioxide  and 
water.  As  much  as  58  per  cent,  of  the  total  protein 
may  be  converted  into  carbohydrate,  a  fact  which  is  of 
importance  in  diabetic  feeding  (see  page  126).  Protein 
may  thus  take  the  place  of  carbohydrate  or  fat  as  a 
source  of  energy,  apart  from  its  function  of  tissue  building, 
but  it  must  be  remembered  that  its  use  for  that  purpose 
is  wasteful  both  of  material  and  cell  activity,  since  so 
large  a  proportion  of  the  protein  molecule  remains  com- 
bined with  the  nitrogen  and  is  excreted  without  giving 
up  its  energy  to  the  system.  Moreover  there  is  reason 
to  believe  that  the  unnecessary  strain  on  the  organs 
engaged  in  deaminizing  and  excreting  large  quantities 
of  protein  is  injurious. 

Carbohydrates. — The  monosaccharides  pass  into  the 
blood  on  absorption  and  are  carried  directly  to  the  liver 
where  they  are  built  up  into  a  new  carbohydrate  com- 
plex, glycogen,  which  is  stored  up  in  the  liver  and  de- 
composed into  dextrose  as  required.  The  muscles  also 
contain  glycogen,  and  during  exercise  this  glycogen  is 
hydrolyzed  to  dextrose  which  is  then  further  decomposed 
to  carbon  dioxide  and  water,  setting  free  chemical 
energy  which  the  muscles  convert  into  mechanical  en- 
ergy. The  supply  of  glycogen  in  the  muscle  is  thus  de- 
pleted, but  the  muscle  supplies  the  deficiency  by  taking 
dextrose  from  the  blood  (which  always  contains  about 


PHYSIOLOGICAL  CHEMISTRY  125 

1  per  cent.)  and  building  this  up  into  more  glycogen. 
As  the  blood  becomes  poorer  in  dextrose  however,  more  of 
the  glycogen  of  the  liver  is  decomposed  into  dextrose 
which  passes  into  the  blood,  only  to  be  taken  up  by  the 
muscles  again.     There  is  therefore  an  automatic  regula- 
tion by  which  the  supply  of  carbohydrate  in  the  blood 
and  muscles  is  kept  constant  by  the  liver.     This  organ 
only  contains  as  a  rule  about  one-third  of  a  pound  of 
carbohydrate,  and  about  as  much  more  is  distributed 
through  the  muscles,  along  with  a  very  small  amount  in 
the  blood.     The  total  carbohydrate  content  of  a  body  at 
rest  is  therefore  something  less  than  one  pound,  and  this 
amount  may  be  greatly  reduced  by  exercise  or  exposure 
to  cold.     The  amount  taken  in  the  food  must  maintain 
this  level  in  the  body  and  supply  any  excess  that  may  be 
called  for  by  the  day's  activity.     If  more  than  this  is 
taken  in,  under  suitable  conditions,  it  is  transformed  into 
fat   and  stored  in   that  form;  hence   the  well-known 
fattening  power  of  carbohydrate  food.     On  the  other 
hand,  if  such  a  large  excess  of  carbohydrate  is  taken  that 
the  system  can  neither  use  it  as  carbohydrate  nor  trans- 
form it  sufficiently  quickly  into  fat  it  is  excreted  through 
the  kidneys  and  appears  as  dextrose  in  the  urine,  where 
it  may  readily  be  detected  by  the  Fehling  test  (see  page 
98) .    This  phenomenon  is  frequently  observed  soon  after 
a  large  amount  of  carbohydrate  has  been  eaten  and 
is  then   called  alimentary  glycosuria.     It  is  especially 
likely  to  occur  if  the  carbohydrate  of  the  food  is  present 
in  the  form  of  sugar,  since  starch  requires  a  much  longer 
time  for  its  hydrolysis  and  is  therefore  absorbed  more 
gradually.     Dextrose  is  even  more  rapidly  assimilated 
than   are   the  disaccharides,   and  for  this  reason  and 
because  it  is  less  sweet  than  cane  sugar  there  is  a  little 
more  danger  of  constant  over-eating  of  this  form  of 
carbohydrate    if    it    is    used    in  unrestricted  amounts. 


126  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

This  is  the  only  legitimate  objection  that  could  be  made 
to  glucose  as  a  food  and  is  the  chief  reason  for  legislating 
against  its  indiscriminate  use  by  confectioners  and 
bakers. 

While  the  above  mentioned  alimentary  glycosuria  is 
merely  temporary  and  is  of  no  consequence  except  inas- 
much as  it  is  a  waste  of  food  material,  a  chronic  glycos- 
uria or  elimination  of  sugar  is  one  of  the  symptoms  of 
the  disease  known  as  diabetes.  Accompanying  symptoms 
are  increase  in  the  sugar  content  of  the  blood » and  ap- 
pearance of  acetone  derivatives,  chiefly  of  an  acid  char- 
acter, in  the  urine,  a  condition  which  is  known  as  acidosis 
and  is  believed  to  be  due  to  the  imperfect  combustion  of 
fats  and  proteins.  It  should  be  noted,  however,  that 
very  fat  people  without  any  diabetic  tendency  are  prone 
to  acidosis,  due  to  the  excessive  amount  of  fat  which  they 
decompose,  while  on  the  other  hand  very  thin  people 
show  the  same  tendency  on  account  of  excessive  decom- 
position of  protein  in  their  bodies. 

The  cause  of  diabetes  is  still  undetermined,  but  enough 
has  been  learned  to  point  the  way  to  various  forms  of 
treatment  which  have  been  used  with  considerable  suc- 
cess. Administration  of  sodium  bicarbonate  is  found  to 
be  effective  in  counteracting  the  tendency  to  acidosis, 
while  the  excretion  of  sugar  can  be  largely  controlled  by 
careful  diet  and  exercise.  In  the  early  history  of  the 
disease  it  was  believed  sufficient  to  restrict  the  carbo- 
hydrate food  and  allow  the  patient  to  get  all  his  nourish- 
ment from  fats  and  proteins,  but  this  treatment  was  only 
better  than  none  at  all.  That  it  could  not  be  really 
satisfactory  will  be  evident  when  we  consider  that  about 
50  per  cent,  of  the  protein  consumed  may  be  converted 
into  glucose  and  the  remainder  may  go  to  increasing  the 
amount  of  acetone  bodies  present,  while  fats,  although 
they  do  not  increase  the  glucose  excretion,  do  increase 


PHYSIOLOGICAL  CHEMISTRY  127 

acidosis.  There  must  therefore  be  a  general  reduction  in 
the  total  food  until  the  urine  is  sugar  free,  when  the 
diet  may  be  slowly  increased.  In  the  Allen  treatment 
which  has  been  used  with  notable  success  in  this  country 
the  patient  is  first  made  to  undergo  a  prolonged  fast  until 
the  excretion  of  sugar  stops  completely.  This  rests  the 
weakened  functions  and  is  found  to  be  very  beneficial 
even  in  cases  where  the  patient  is  emaciated  at  the  start. 
During  this  fasting  period  water  is  given  freely,  along 
with  a  little  clear  tea  or  coffee  if  desired.  Some  phy- 
sicians prefer  to  give  a  little  food  after  two  or  three  days 
and  then  recommence  the  fast,  others  prescribe  one  un- 
broken fast  until  the  desired  result  is  obtained.  The 
diet  is  then  very  carefully  regulated,  the  food  being  in- 
creased very  slowly,  with  frequent  tests  to  show  whether 
any  sugar  is  being  excreted.  At  the  reappearance  of  a 
trace  of  sugar  the  fast  is  repeated  until  it  disappears 
again  and  the  feeding  is  then  begun  at  a  lower  level  than 
the  point  at  which  it  was  stopped  and  increased  still 
more  gradually.  Under  these  conditions  a  tolerance  is 
established  first  for  carbohydrate,  then  for  protein,  and 
lastly  for  fat.  After  this  point  has  been  reached  reason- 
able care  and  self  control  on  the  part  of  the  patient 
is  usually  sufficient  to  keep  the  disease  latent,  but  over 
feeding  will  not  only  cause  the  reappearance  of  sugar 
but  also  acidosis  and  the  condition  may  be  even  worse 
than  before  treatment. 

For  the  normal  person  sugar,  owing  to  the  ease  and 
rapidity  with  which  it  can  be  digested  and  assimilated, 
is  a  prompt  and  efficient  stimulant,  especially  in  case  of 
muscular  fatigue.  The  reviving  effect  of  a  cup  of  hot 
chocolate  on  a  cold  day  is  partly  due  to  the  warming 
up  of  the  body  by  the  hot  liquid  and  partly  to  the 
rapidly  absorbed  carbohydrate  which  replaces  the  stores 
depleted  by  cold  and  exertion. 


CHAPTER  XXI 

THE  ENERGY  OF  THE  BODY 

Since  any  form  of  energy  can  be  converted  into  any 
other  form  and  since  if  the  transformation  be  properly 
carried  out  there  will  be  no  loss  of  energy,  it  follows 
that  a  given  amount  of  mechanical  energy  is  equivalent 
to  a  given  amount  of  heat  energy  and  vice  versa.  So 
if  we  know  how  much  heat  a  piece  of  coal  will  give  out 
we  can  calculate  how  much  water  it  will  convert  into 
steam  and  what  load  that  steam  will  lift;  in  other  words, 
we  can  express  the  heat  value  of  the  coal  in  terms  of 
mechanical  energy.  On  the  other  hand,  when  a  hammer 
falls  on  an  anvil  it  produces  a  certain  amount  of  heat, 
the  amount  being  proportional  to  the  weight  of  the 
hammer  and  the  height  from  which  it  falls,  so  that  the 
mechanical  energy  of  the  blow  can  be  expressed  in 
terms  of  heat  energy. 

In  order  to  measure  anything  it  is  necessary  to  have 
some  unit  of  measurement.  There  are  various  units 
of  weight  in  common  use,  the  ounce,  the  gram,  the  grain, 
etc.  We  may  measure  length  in  inches,  or  feet,  or  yards. 
To  express  volume  we  have  the  pint,  the  liter,  and  so 
on.  Similarly  we  measure  amounts  of  heat  in  Calories. 
The  Calorie  is  the  amount  of  heat  which  will  heat  one 
pound  of  water  just  about  4°F. 

Since  the  main  function  of  the  food  is  to  provide  energy 
for  the  organism  it  becomes  of  importance  to  be  able 
to  calculate  the  energy  value  of  any  food,  and  this  can 
be  done  by  ascertaining  how  much  heat  it  will  give  out 
when  it  is  decomposed  in  the  body.  Since  the  sum  total 

128 


PHYSIOLOGICAL  CHEMISTRY  129 

of  the  changes  undergone  by  the  food  in  the  body  results 
in  its  oxidation  the  problem  resolves  itself  into  the  deter- 
mination of  how  much  heat  a  given  amount  of  protein 
will  give  out  when  it  is  oxidized,  or  burned.  This  can 
be  done  by  making  use  of  an  appliance  called  a  calori- 
meter which  consists  of  a  steel  tube  in  which  a  weighed 
amount  of  food  is  placed  and  which  is  then  filled  with 
oxygen  and  sealed  up.  This  is  immersed  in  an  outer 
vessel  filled  with  water  and  so  arranged  that  no  heat  can 
get  into  it  except  from  the  inner  tube,  or  out  from  it  to 
the  outside  air.  The  food  in  the  inner  tube  is  then 
ignited  by  means  of  an  electric  spark  and  allowed  to  burn. 
The  heat  produced  warms  the  water  in  the  outside  vessel 
and  by  weighing  the  water  and  noting  the  number  of 
degrees  of  temperature  change  the  number  of  Calories 
given  off  by  the  food  in  burning  can  be  determined. 
Moreover,  it  has  been  found  possible  to  devise  an  en- 
larged calorimeter  on  somewhat  the  same  plan,  in  which 
a  human  being  can  be  placed  and  where  the  heat  given 
off  from  the  body  can  be  measured,  as  welt  as  the  carbon 
dioxide  and  water  eliminated  from  the  lungs  and  skin 
and  the  oxygen  used  up  in  metabolism.  By  means  of  this 
appliance  it  has  been  found  that  the  heat  given  off  in  the 
oxidation  of  carbohydrate  and  fat  is  exactly  the  same 
whether  they  are  burned  in  the  body  or  outside  it.  The 
heat  given  off  by  a  burning  substance  is  called  its  heat 
of  combustion.  This  heat  is  found  to  be  about  113 
Calories  per  ounce  for  carbohydrates  and  proteins  and 
about  255  Calories  per  ounce  for  fats.  Proteins  give 
off  a  little  less  heat  in  the  body  than  when  burned 
outside  it,  owing  to  the  excretion  of  incompletely  oxidized 
products,  but  when  a  correction  is  made  for  these  the 
agreement  is  truly  remarkable,  considering  the  difficulty 
of  making  accurate  observations  of  this  sort. 

With  the  help  of  the  calorimeter  it  is  possible  to  find 


130  CHEMISTBY  FOR  NURSES  AND  STUDENTS 

out  how  much  energy  is  being  used  up  in  various  kinds 
of  exercise,  and  even,  by  calculating  the  relative  amounts 
of  oxygen  used  up  and  of  carbon  dioxide  and  nitrogen 
compounds  excreted,  to  determine  accurately  what  kind 
of  material  is  being  oxidized  to  produce  this  energy. 
Many  interesting  and  important  facts  about  human 
metabolism  have  been  learned.  It  has  been  proved  that 
the  body  can  obtain  its  energy  from  either  carbohydrate, 
fat,  or  protein,  and  therefore  these  substances  can  replace 
each  other  in  the  diet  to  an  extent  proportional  only  to 
their  energy  value;  that  is,  since  an  ounce  of  carbo- 
hydrate gives  a  little  less  than  half  as  much  heat  as  an 
ounce  of  fat,  half  an  ounce  of  the  latter  will  more  than 
replace  one  ounce  of  carbohydrate.  This  is  known  as 
the  Law  of  Isodynamics,  and  is  of  great  importance  to 
the  dietician  since  it  means  that  a  diet  may  be  widely 
varied  according  to  taste  or  convenience,  provided  the 
energy,  or  fuel  value,  of  the  food  remains  unchanged. 
This  law  must,  however,  be  used  with  certain  restric- 
tions. Neither  fat  nor  carbohydrate,  could  be  entirely 
substituted  for  protein,  since  neither  of  these  contains 
the  essential  nitrogen  which  the  tissues  require.  If  fat 
and  carbohydrate  are  lacking,  the  necessary  energy  can 
be  obtained  from  protein  alone,  and  on  the  other  hand, 
if  they  are  present  in  abundance  much  less  protein  is 
broken  down,  as  is  shown  by  the  decreased  amount  of 
nitrogen  compounds  in  the  urine.  Moreover,  as  has 
been  already  pointed  out,  two  kinds  of  protein  are  not 
necessarily  of  equal  value  even  though  their  fuel  value 
is  the  same,  since  one  may  have  a  better  proportion 
than  the  other  of  the  amino  acids  which  the  tissues 
require. 


CHAPTER  XXII 
THE  BLOOD 

Just  as  the  nerves  may  be  regarded  as  the  telephone  or 
telegraph  system  by  which  messages  are  sent  from  one 
part  of  the  body  to  another,  so  the  blood  corresponds 
to  the  express  service  by  which  materials  of  all  kinds  can 
be  transported  from  place  to  place.  Food  materials 
must  be  carried  from  the  digestive  tract  and  oxygen  from 
the  lungs.  Various  organs  produce  secretions  which 
stimulate  or  modify  the  action  of  other  organs,  and  these 
secretions  are  taken  by  the  blood  to  the  point  of  appli- 
cation. Waste  materials  must  be  carried  from  the  tis- 
sues to  the  excreting  organs.  The  great  convenience  of 
a  rapidly  circulating  medium  like  the  blood  which  can 
dissolve  some  substances  and  absorb  or  combine  with 
others  to  form  compounds  which  are  easily  separated 
again  is  obvious. 

The  blood  consists  of  a  liquid  portion,  the  plasma, 
in  which  float  large  numbers  of  living  cells,  the  corpuscles. 
The  plasma  is  a  clear  yellowish  fluid  of  which  about  nine- 
tenths  is  water,  and  the  remainder  chiefly  protein,  with 
about  1  per  cent,  of  inorganic  salts  and  small  quantities 
of  other  substances  such  as  dextrose,  fatty  substances, 
nitrogen  compounds,  etc.  Blood  freshly  drawn  is 
perfectly  fluid,  but  on  standing  it  clots  or  coagulates  in 
the  course  of  from  2  to  10  minutes  into  a  dark  red  jelly- 
like  solid,  from  which  a  little  yellowish  liquid,  the  serum, 
separates,  very  like  the  plasma  in  appearance,  but  with 
lower  protein  content.  The  clot  is  found  to  consist 
of  a  very  fine  net-work  of  fibrin,  a  protein  substance 

131 


132  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

separated  from  the  plasma,  in  which  the  corpuscles  are 
emmeshed  and  held.  If  instead  of  allowing  the  blood  to 
stand  quietly  it  is  vigorously  stirred  or  beaten  the  fibrin 
separates,  but  not  in  such  a  fine  net,  so  that  the  corpus- 
cles instead  of  being  held  in  a  clot  remain  suspended  in 
the  serum.  This  suspension  of  corpuscles  in  plasma  from 
which  the  fibrin  has  been  removed  is  called  defibrinated 
blood.  The  clotting  of  blood  is  a  property  of  greatest 
importance,  since  the  formation  of  a  clot  stops  bleeding 
and  so  prevents  fatal  hemorrhage.  It  seems  to  be  of 
the  nature  of  a  crystallization  of  the  fibrin,  but  authori- 
ties are  undecided  as  to  its  cause.  The  presence  of 
calcium  salts  is  essential  for  clotting  and  the  action  is 
greatly  hastened  by  contact  with  the  wounded  tissue 
or  with  some  foreign  substance  which  seems  to  act  as 
the  foundation  on  which  the  deposition  of  the  fibrin 
can  begin.  The  use  of  cobwebs  to  stop  bleeding,  as  was 
done  in  olden  days,  depended  on  this  principle,  but  was 
of  course  very  dangerous  owing  to  the  likelihood  of 
infecting  the  wound.  Anaesthetics  render  the  blood 
abnormally  easy  to  clot,  and  hemorrhages  have  the  same 
effect  so  that  clotting  in  the  veins  of  the  legs,  particularly 
in  the  right  leg,  is  not  unusual,  for  instance  after  par- 
turition or  an  appendicitis  operation.  The  condition 
known  as  "milk  leg"  is  the  result  of  such  a  clot  becoming 
fixed  and  disturbing  the  circulation  of  the  leg. 

Hemophilia  is  a  derangement  of  the  blood  which  pre- 
vents clotting,  so  that  people  have  been  known  to  bleed 
to  death  from  so  small  a  wound  as  that  made  by  pulling  a 
tooth.  It  is  inheritable,  and,  curiously,  is  usually 
transmitted  by  the  females  but  appears  in  the  male 
members  of  the  family. 

The  erythrocytes,  or  red  corpuscles  of  the  blood,  are 
small  gelatinous  discs,  slightly  hollowed  out  on  the  sur- 
face, with  a  diameter  of  about  one-thirty-two  hundredth 


PHYSIOLOGICAL  CHEMISTRY  133 

of  an  inch,  and  a  thickness  of  about  one-fifth  as  much. 
The  blood  of  the  adult  male  normally  contains  from 
5-6,000,000  per  c.mm.,  that  of  females  from  4-4,500,000, 
but  in  anemia  the  number  may  be  reduced  to  less  than 
half  of  this.  On  the  other  hand  they  are  increased  by 
massage,  by  hot  or  cold  baths,  by  the  administration  of 
certain  drugs,  and  in  diseases  such  as  cholera,  diarrhea, 
and  dysentery. 

The  most  important  constituent  of  the  red  corpuscles  is 
the  hemoglobin,  or  red  coloring  matter,  which  has  the 
power  of  combining  with  oxygen  to  form  a  very  unstable 
compound  which  is  called  oxy-hemoglobin  and  which 
very  readily  gives  up  its  oxygen  to  the  tissues.  Qxy- 
hemoglobin  is  bright  red  in  color,  while  hemoglobin  has  a 
darker,  purplish  shade,  hence  the  difference  in  color 
between  blood  flowing  from  the  arteries,  which  convey 
the  blood  from  the  lungs  to  the  tissues,  and  that  from 
the  veins,  which  carry  it  from  the  tissues  to  the  lungs 
again.  Hemoglobin  is  a  very  complex  protein  substance 
containing  iron.  With  an  insufficient  amount  of  iron 
in  the  food  formation  of  hemoglobin  decreases.  Addition 
of  iron  salts  greatly  influences  the  production  of  red 
corpuscles,  and  especially  the  amount  of  hemoglobin 
they  contain,  but  their  method  of  action  is  obscure. 
With  regard  to  the  oxygen  carrying  power  of  hemoglobin 
little  can  be  added  to  what  has  already  been  said,  that 
hemoglobin  has  the  power  of  uniting  with  oxygen  and 
giving  it  off  again  to  the  tissues  (see  page  17).  That  the 
oxygen  is  actually  chemically  combined  and  not  merely 
dissolved  in  the  blood  is  proved  by  the  large  amount  of 
oxygen  present  in  arterial  blood  as  compared  with  the 
amount  which  will  dissolve  in  the  blood  serum.  Hemo- 
globin can  combine  with  other  gases  also,  notably  carbon 
monoxide.  When  blood  has  been  exposed  to  a  mixture 
of  this  gas  with  oxygen  or  air  the  hemoglobin  combines 


134  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

with  the  carbon  monoxide  rather  than  with  the  oxygen, 
thus  preventing  the  usual  supply  of  oxygen  from  reaching 
the  tissues.  50  per  cent,  saturation  with  carbon  mon- 
oxide endangers  the  life  of  an  animal,  and  with  human 
beings  this  can  occur  in  the  presence  of  as  little  as  0.05 
per  cent,  of  carbon  monoxide  in  the  ah*.  The  fatal 
effect  of  prolonged  exposure  to  coal  gas  is  largely,  if 
not  entirely,  due  to  the  carbon  monoxide  present. 

Owing  to  the  vast  number  of  corpuscles  and  their 
peculiar  shape  they  expose  a  very  large  surface  to  the 
action  of  the  oxygen.  It  is  calculated  that  under  normal 
conditions  the  combined  area  of  the  red  corpuscles  in  an 
adult  man  would  be  about  3520  sq.  yds.  representing 
between  one  and  two  pounds  of  hemoglobin.  The 
advantage  of  having  this  surface  distributed  among  a 
great  many  smaller  particles  instead  of  among  a  smaller 
number  of  larger  particles  is  partly  because  of  the  ease  of 
transportation  through  the  small  passages  and  partly 
because  of  the  great  rapidity  with  which  they  can  be 
loaded  and  unloaded  with  oxygen. 

If  the  corpuscles  are  dissolved  or  injured  so  that  the 
hemoglobin  escapes  into  the  plasma  the  blood  is  said  to 
be  laked,  and  the  destruction  of  the  corpuscles  in  this 
manner  is  called  hemolysis.  Hemolysis  may  be  brought 
about  by  immersing  the  corpuscles  in  water  or  in  a 
hypotonic  salt  solution  (see  page  26),  or  by  the  action 
of  chemical  substances,  including  the  products  of  bac- 
terial life  and  the  poison  of  snake  bites,  spider  and  bee 
stings,  etc. 

The  white  corpuscles  or  leucocytes  are  somewhat  larger 
than  the  red  corpuscles  and  are  present  in  the  proportion 
of  about  one  of  the  former  to  350-500  of  the  latter. 
They  behave  like  independent  organisms  and  are  capable 
of  spontaneous  movement,  so  that  they  can  enter  and 
leave  the  blood  and  penetrate  the  tissues  at  will.  Their 


PHYSIOLOGICAL  CHEMISTRY  135 

most  remarkable  property  is  the  power  of  absorbing 
solid  particles  of  tissue,  food  substances,  bacteria,  etc. 
Since  they  assemble  in  large  numbers  around  the  diges- 
tive tract  during  the  process  of  digestion  it  has  been 
suggested  that  they  may  help  to  carry  the  products  of 
digestion  through  the  system,  but  their  main  function  is 
believed  to  be  the  removal  of  old,  worn-out  or  diseased 
tissues  and  cells,  and  to  digest  or  destroy  injurious 
organisms  which  find  their  way  into  the  tissues.  The 
power  of  the  leucocytes  to  destroy  bacteria  in  this  way 
seems  to  be  connected  with  the  presence  in  the  blood 
of  certain  substances  called  opsonins.  The  higher  the 
opsonic  index,  that  is,  the  greater  the  content  of  opsonins 
in  the  blood  the  greater  will  be  the  resistance  of  the  body 
to  bacterial  infection.  Increase  in  the  number  of  leuco- 
cytes present  in  the  blood  is  known  as  leucocytosis,  and 
is  found  as  an  accompaniment  of  many  disorders. 

Besides  conveying  oxygen  to  the  tissues  the  blood 
carries  carbon  dioxide  from  the  tissues  to  the  lungs  for 
excretion.  This  carbon  dioxide  is  partly  dissolved 
in  the  blood,  partly  present  in  the  form  of  sodium  bicar- 
bonate, and  partly  combined  with  the  blood  proteins. 
The  presence  of  carbon  dioxide  in  the  blood  decreases 
the  affinity  of  the  corpuscles  for  oxygen  and  hence  as  the 
blood  travels  through  the  tissues  and  gathers  up  carbon 
dioxide  it  tends  to  give  up  the  oxygen  which  it  holds  in 
combination.  When  it  reaches  the  lungs,  on  the  other 
hand,  the  carbon  dioxide  escapes  and  the  corpuscles 
have  now  increased  power  of  taking  up  oxygen. 


CHAPTER  XXIII 
EXCRETIONS  OF  THE  BODY 

The  waste  material  leaves  the  body  by  way  of  the  lungs, 
the  skin,  the  feces,  and  the  urine.  Through  the  lungs 
we  lose  chiefly  the  carbon  dioxide  formed  in  combustion. 
The  perspiration  of  the  skin  consists  mainly  of  water  with 
some  inorganic  salts  and  a  variety  of  organic  substances 
present  in  small  traces,  and  is  mixed  with  the  oily  secre- 
tion of  the  sebaceous  glands.  The  chief  function  of  the 
perspiration  seems  to  be  to  assist  in  the  regulation  of  the 
body  temperature  by  supplying  moisture  which  evaporates 
more  rapidly  as  the  body  becomes  heated,  and  in  so 
doing  removes  the  excess  of  heat.  It  is  a  well  known  fact 
that  those  persons  who  perspire  freely  suffer  less  in  hot 
weather  than  those  whose  sweat-glands  are  less  active. 
The  oily  product  from  the  sebaceous  glands  is  probably 
not  to  be  regarded  as  excreted  waste  but  as  a  true  se- 
cretion which  affords  a  protective  covering  for  the  skin 
and  hairs. 

In  the  feces  the  undigested  residue  of  the  food  is 
removed,  together  with  any  food  material  which  has 
not  been  completely  digested  or  assimilated,  and  consid- 
erable quantities  of  bacteria  from  the  intestines.  Chemi- 
cal and  microscopic  examination  of  the  feces  in  order  to 
detect  pathological  variations  from  the  normal  product 
is  often  valuable  for  diagnostic  purposes.  For  such 
purpose  the  patient  is  usually  kept  on  a  simple  standard 
diet  such  as  the  following1  for  the  experimental  period. 

1  Used  by  Dr.  Rehfus  at  Jefferson  Hospital,  Philadelphia. 

136 


PHYSIOLOGICAL  CHEMISTRY  137 

BREAKFAST:  100  grams  cream-of- wheat  or  oatmeal 
60  grams  toast 
20  grams  butter 
250  c.c.  milk 

LUNCHEON:   Chicken  broth  with  rice 

100  grams  green  vegetable 
100  grams  mashed  potatoes 

60  grams  toast 

20  grams  butter 
250  c.c.  milk 

4  O'CLOCK:     250  c.c.  milk 

DINNER:        150  grams  of  chopped  meat 
100  grams  green  vegetable 
100  grams  mashed  potatoes 

60  grams  toast 

20  grams  butter 
250  c.c.  milk 
Stewed  fruit 

The  patient  is  made  to  swallow  a  gelatine  capsule  con- 
taining powdered  charcoal  or  some  colored  substance 
which  will  give  a  zone  of  color  to  the  fecal  mass  at 
the  beginning  and  end  of  the  experimental  period, 
thus  serving  to  separate  the  feces  of  that  period  from 
those  produced  before  and  after.  A  similar  method  is 
resorted  to  in  nutrition  and  metabolism  experiments- 
in  order  to  be  able  to  calculate  accurately  the  output 
through  the  feces  in  a  given  period  of  time. 

The  urine  is  the  medium  through  which  the  waste 
nitrogenous  material  passes  out  of  the  body.  Much 
can  be  learned  about  the  process  of  metabolism  from  a 
study  of  these  waste  substances,  and  in  particular,  varia- 
tions from  the  normal  course  can  be  fairly  easily  detected. 
Consequently  careful  study  of  the  urine  is  of  great  as- 
sistance to  the  physician  in  diagnosis.  For  this  purpose 
the  whole  volume  of  urine  passed  in  twenty-four  hours  is 
usually  collected  and  a  sample  of  the  mixed  output  taken 


138  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

for  analysis  in  order  to  avoid  misleading  results  due  to 
temporary  variation  on  account  of  some  superficial 
change  in  conditions.  Little,  if  anything,  can  be  learned 
from  tests  made  on  a  single  sample.  In  certain  patholo- 
gical conditions  it  is  necessary  to  examine  separately  and 
compare  the  urine  passed  during  the  day  and  that  se- 
creted at  night.  When  this  is  done,  that  passed  between 
8  A.M.  and  8  P.M.  may  be  taken  as  the  day  sample  and 
that  from  8  P.M.  to  8  A.M.  as  the  night  sample. 

One  of  the  most  interesting  of  nitrogenous  substances 
excreted  in  the  urine  is  uric  acid.  It  is  produced  partly 
by  direct  decomposition  of  certain  protein  substances, 
called  purines,  in  the  food,  and  partly  as  a  result  of  the 
normal  metabolism  of  the  tissues.  That  coming  from 
the  food  is  sometimes  distinguished  as  exogenous  uric 
acid,  while  that  produced  from  the  tissues  is  called  endo- 
genous. The  exogenous  acid  will  naturally  vary  according 
to  the  amount  and  kind  of  food  eaten,  while  the  endo- 
genous is  dependent  on  the  conditions  of  metabolism. 
In  order  to  study  the  production  of  endogenous  acid  it  is 
necessary  to  experiment  with  subjects  from  whose  diet 
all  food  which  might  give  rise  to  uric  acid  has  been  care- 
fully eliminated.  Under  these  conditions  it  is  found  that 
the  excretion  of  uric  acid  is  greatly  increased  in  diseases 
involving  decomposition  of  the  tissues,  for  instance  after 
extensive  burns  when  the  dead  tissue  is  being  absorbed, 
or  after  the  crisis  in  pneumonia  when  the  exudate  of  the 
lungs  is  undergoing  reabsorption. 

If  through  over  production  or  faulty  excretion  uric 
acid  is  allowed  to  accumulate  in  the  body,  the  various 
unpleasant  symptoms  classed  as  the  uric  acid  disorders 
follow.  Sometimes  the  excess  of  acid  is  deposited  as 
crystals  in  the  kidneys  or  bladder,  a  condition  known 
as  "gravel;"  sometimes  the  deposit  occurs  in  the  joints, 
giving  rise  to  gouty  symptoms;  sometimes  the  excess  is 


PHYSIOLOGICAL  CHEMISTRY  139 

more  generally  distributed  and  the  condition  is  known  as 
lithemia,  and  is  characterized  by  various  forms  of  irri- 
tation of  the  nervous  system,  digestive  disturbances, 
chronic  headaches,  and  occasionally  skin  affections. 

A  patient  suffering  from  excess  of  uric  acid  should  al- 
ways remain  under  the  supervision  of  a  good  physician 
who  will  direct  his  diet  among  other  things,  but  the  gen- 
eral principles  to  be  followed  may  be  indicated.  Since 
the  digestive  system  is  usually  disturbed  by  the  surplus 
of  acid  in  the  system,  all  extra  strain  caused  by  over  in- 
dulgence in  food  should  be  avoided.  All  indigestible 
foods,  and  in  particular  any  food  which  tends  to  be  con- 
stipating or  to  increase  intestinal  putrefaction  will  be 
injurious.  Alcohol  tends  to  hinder  uric  acid  elimination 
and  is  therefore  forbidden,  except  in  the  case  of  elderly 
or  debilitated  patients  for  whom  stimulation  is  abso- 
lutely necessary,  when  whiskey  is  sometimes  ordered. 

Since  uric  acid  is  produced  from  purines  it  is  of  course 
desirable  to  eliminate  from  the  diet  as  far  as  possible  all 
foods  containing  these  substances.  In  general  meats 
contain  more  purines  than  vegetable  food.  Sweet- 
breads, kidney,  and  liver  are  particularly  rich  in  purines 
and  should  be  avoided  entirely,  while  other  meats  should 
be  used  very  sparingly  if  at  all.  Boiling  removes  some  of 
the  purines  and  accordingly  boiled  meats  are  sometimes 
allowed  in  small  amounts  when  roast  or  fried  meats  are 
forbidden.  Fish,  with  the  exception  of  cod,  are  fairly 
high  in  purine  content,  sardines  and  anchovies  particu- 
larly so.  Green  vegetables  are  practically  purine  free, 
with  the  exception  of  spinach,  asparagus,  peas,  and  beans, 
and  even  these  exceptions  contain  less  than  meat  or  fish. 
Milk,  eggs,  cheese,  nuts,  cereals,  root  vegetables,  and 
fruits  may  all  be  regarded  as  purine  free. 

Many  physicians  forbid  certain  vegetables,  not  because 
they  contain  purines  but  because  they  contain  an  acid, 


140  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

oxalic  acid,  which  is  believed  to  aggrevate  the  uric  acid 
disturbances.  Among  these  forbidden  vegetables  are 
rhubarb,  asparagus,  tomatoes,  sweet  potatoes,  and  mush- 
rooms. With  regard  to  fruit  authorities  differ  consider- 
ably, but  nearly  all  agree  in  allowing  apples,  pears, 
peaches,  oranges,  and  pineapples,  and  forbidding  straw- 
berries on  accoun  t  of  the  acid  which  they  contain .  Where 
cooked  fruits  are  permitted  they  are  generally  stewed 
without  sugar  so  that  they  may  be  less  likely  to  undergo 
fermentation  in  the  process  of  digestion.  In  order  to 
make  such  fruits  palatable  they  may  be  sweetened  with 
saccharine,  a  substance  which  has  a  very  sweet  taste 
but  has  no  other  relation  to  sugar. 


SECTION  IV 

PRACTICAL  MANUAL 
CHEMICALS  WHICH  REQUIRE  SPECIAL  CARE  IN  HANDLING 

Potassium  and  sodium  react  with  water  with  explosive 
violence.  They  are  best  preserved  under  kerosene  oil, 
care  being  taken  to  see  that  they  are  well  under  the  sur- 
face of  the  oil.  Never  throw  potassium  or  sodium  into 
the  sink  or  waste  jar.  Always  handle  these  metals  with 
forceps,  never  with  the  fingers. 

Phosphorus  oxidizes  so  rapidly  in  the  air  that  it  may 
take  fire  spontaneously.  It  is  therefore  always  kept 
under  water.  This  statement  and  the  one  in  the  pre- 
ceding paragraph  should  be  carefully  noted,  as  serious  ac- 
cidents have  occurred  through  careless  confusing  of  the 
two,  and  attempting  to  put  sodium  in  a  jar  of  water. 
Phosphorus  inflicts  severe  burns  if  it  comes  in  contact 
with  the  skin.  The  greatest  care  should  be  exercised 
to  prevent  this  but  in  case  of  accident  remember  that 
the  first  aid  treatment  for  such  a  burn  is  with  water  in 
copious  quantities,  never  oil. 

Bromine  is  another  element  which  inflicts  severe  burns. 
Here  again  the  first  treatment  in  case  of  accident  is  with 
large  quantities  of  water,  which  should  be  applied  as 
quickly  as  possible.  Even  a  slight  bromine  burn  should 
be  shown  to  a  physician  at  once,  as  an  apparently  super- 
ficial burn  may  develop  into  a  severe  injury  if  not  prop- 
erly treated. 

141 


142  CHEMISTRY  FOB  NURSES  AND  STUDENTS 

All  strong  acids  burn,  but  NITRIC  ACID  burns  are  the 
most  serious,  being  comparable  to  those  of  bromine  and 
phosphorus.  Even  dilute  acids  eat  through  cotton 
rapidly,  but  they  have  little  effect  on  woolens  except  to 
change  the  color.  This  can  sometimes  be  restored 
by  sponging  with  dilute  ammonia. 

When  concentrated  SULPHURIC  ACID  is  mixed  with 
water  a  large  amount  of  heat  is  developed.  If  a  little 
water  is  added  to  the  strong  acid  it  does  not  diffuse 
sufficiently  rapidly  through  the  heavy  acid  and  the  heat 
developed  may  be  sufficient  to  convert  the  water  into 
steam,  with  the  result  that  the  strong  acid  is  thrown  out 
of  the  containing  vessel.  In  making  a  solution  of  sul- 
phuric acid  therefore  the  acid  should  always  be  poured 
into  the  water  with  constant  stirring.  Under  these  con- 
ditions there  is  no  danger  of  accident. 

Alkalies  have  a  very  unpleasant  effect  on  the  skin, 
but  do  not  actually  burn  except  when  hot,  or  in  the 
mouth  or  eyes.  In  such  a  case  wash  well  with  water  and 
then  with  a  very  dilute  solution  of  acetic  acid  or  vinegar. 
Alkalies  do  not  destroy  cotton,  but  readily  attack  wool. 
They  maybe  carefully  neutralized  in  the  fabric  with  dilute 
hydrochloric  or  acetic  acid,  care  being  taken  to  wash  out 
the  acid  afterwards. 

Ether  is  not  only  a  highly  inflamable  liquid  but  very 
volatile  as  well,  giving  off  a  vapor  which  when  mixed 
with  air  is  explosive.  Ether  should  therefore  never  be 
handled  anywhere  in  the  vicinity  of  a  flame,  and  every 
care  should  be  taken  to  prevent  the  escape  of  the  vapor 
into  a  room.  So  small  a  thing  as  the  spark  caused  by 
turning  on  an  electric  switch  has  been  known  to  cause 
an  explosion  in  a  room  filled  with  ether  fumes. 

Ordinary  GASOLINE  and  the  less  common  PETROLEUM 
ETHER  should  be  treated  with  the  same  care  as  ether. 


PRACTICAL  MANUAL  143 

GENERAL  DIRECTIONS 

Concentrate  first  on  accuracy  in  following  directions, 
then  on  efficiency,  then  on  speed. 

Cultivate  neatness.  Pour  carefully.  Don't  leave 
bottles  with  drops  trickling  down  then*  sides.  Don't 
put  wet  glass  rods,  stoppers  of  bottles,  and  so  on  down 
on  the  table.  Don't  leave  bits  of  paper,  burned  matches, 
etc.,  lying  round.  Try  not  to  spill  water,  but  if  it  should 
get  spilled  wipe  it  up  immediately.  An  untidy  worker 
is  a  poor  worker. 

When  using  a  reagent  bottle  take  the  stopper  between 
the  first  and  second  fingers  of  the  right  hand,  holding  it 
there  while  you  use  the  bottle;  then  replace  it  without 
having  allowed  it  to  come  in  contact  with  anything 
while  it  was  out  of  its  bottle.  This  is  done  to  avoid 
any  possible  contamination  of  the  reagents  through 
misplaced  stoppers. 

Use  common  sense  to  increase  efficiency.  Eliminate 
all  unnecessary  handling  and  holding  of  apparatus, 
walking  round  to  collect  the  necessary  reagents  for  a 
given  experiment,  and  so  on. 

In  heating  a  liquid  contained  in  a  glass  vessel  be  care- 
ful that  the  flame  never  strikes  the  surface  of  the  glass 
above  the  level  of  the  liquid.  This  causes  unequal  ex- 
pansion and  the  glass  will  break.  Flasks  and  beakers 
should  be  supported  on  a  wire  gauze  or  asbestos  mat  in 
order  to  prevent  too  strong  heating. 

In  order  to  avoid  burning  the  fingers  while  heating  a 
test  tube  make  a  holder  by  doubling  a  piece  of  paper 
into  a  strip  about  an  inch  wide  and  folding  it  around 
the  tube  at  the  top,  holding  it  by  the  ends  (see  Fig.  1). 

If  a  liquid  is  heated  strongly  at  one  point,  instead 
of  boiling  quietly  the  bubbles  of  vapor  sometimes  form 
irregularly  and  break  so  violently  that  the  hot  liquid 


144 


CHEMISTRY  FOR  NURSES  AND  STUDENTS 


is  often  spattered  out  of  the  containing  vessel.  This 
is  known  as  " bumping."  In  order  to  avoid  this  it  must 
be  heated  as  uniformly  as  possible,  either  by  keeping 
the  flame  moving  or  by  stirring  the  liquid.  Where 
the  heating  is  done  in  a  test  tube  the  stirring  is  best 
accomplished  by  shaking  the  test  tube  constantly  with 
a  sharp  sideways  jerk  of  the  wrist.  A  little  practice 
will  show  how  this  may  be  done  without  shaking  out 
the  contents.  Never  attempt  to  heat  a  test  tube 
without  shaking.  Where  there  is  so  much  liquid  that 


FIG.  1. 


FIG.  2. 


it  cannot  be  shaken  without  spilling,  use  instead  of  a 
test  tube  a  small  beaker,  the  contents  of  which  may  be 
stirred  with  a  glass  rod.  Bumping  may  also  be  avoided 
by  dropping  into  the  liquid  two  or  three  small  fragments 
of  porcelain  (from  a  broken  plate),  or  better,  of  pipe-clay. 
The  bubbles  form  around  these  and  come  off  more 
regularly. 

Where  heating  is  to  be  done  cautiously  it  is  better 
to  hold  the  burner  in  the  hand,  so  that  the  heat  can  be 
regulated  by  moving  it  about.  When  this  is  done 
always  hold  the  burner  in  a  slanting  position  so  that  the 
hand  will  not  be  directly  under  the  substance  which  is 
being  heated.  In  this  way  there  is  no  danger  of  being 


PRACTICAL  MANUAL 


145 


burned  if  a  flask  or  beaker  should  break  or  its  contents 
should  spatter  out  (see  Fig.  2). 

For  rough  estimations  of  temperature  the  following 
standards  may  be  kept  in  mind.  Melting  ice  is  at  a 
temperature  of  0°C.  Ordinary  room  temperature  aver- 
ages from  17  to  20°C.  Blood  heat  is  about  27°C. 
50° C  is  as  high  a  temperature  as  the  hand  will  bear 
comfortably. 

To  fold  filter  paper.  In  order  to  filter  successfully 
without  wasting  time  it  is  important  to  have  the  filter 
paper  fitted  accurately.  To  accomplish  this,  fold  the 
round  of  paper  first  in  two,  then  in  four,  and  open  up 
the  resulting  triangular  segment  so  that  there  are  three 
thicknesses  of  paper  on  one  side  and  one  on  the  other. 


FIG.  3. 

If  the  cone  thus  obtained  does  not  fit  the  funnel  per- 
fectly it  can  be  enlarged  as  much  as  necessary  by  altering 
the  second  fold  a  little,  so  that  the  edges  do  not  come 
exactly  together  (see  Fig.  3).  To  test  a  filter,  fill  it 
with  water  and  note  the  rapidity  with  which  it  runs 
out.  It  should  run  in  a  steady  stream  which  fills  the 
stem  of  the  funnel,  with  no  air  bubbles. 

To  cut  glass  tubing.  With  a  sharp  file  make  a  fairly 
deep  scratch  about  a  quarter  of  an  inch  long  in  the  glass. 
Take  the  tube  in  both  hands,  scratch  towards  you, 
fingers  outward,  thumbs  about  an  inch  on  either  side  of 
the  scratch,  (see  Fig.  4),  and  bend  the  glass  sharply 
outward,  away  from  the  scratch.  If  it  does  not  break 

10 


146 


CHEMISTRY  FOR  NURSES  AND  STUDENTS 


readily,  cut  the  scratch  a  little  deeper.  Glass  so  cut 
will  have  a  sharp  edge  which  should  be  rounded  off. 
This  may  be  done  by  rasping  it  against  the  flat  side  of  a  file, 
or  better,  by  holding  it  in  the  flame  until  the  edge  softens 
and  rounds.  Remember,  never  put  hot  glass  down  on  a 
cold  surface. 


FIG.  4. 

To  bend  glass  tubing.  Use  an  ordinary  illuminating 
gas  jet  or  a  "fish  tail"  top  on  a  Bunsen  burner,  to  spread 
out  the  flame  over  a  greater  amount  of  surface.  Heat 
the  glass  gently  for  a  minute,  then  more  strongly,  resting 
it  lightly  on  the  fingers  of  both  hands  and  turning  it 
steadily  round  and  round  so  that  it  heats  evenly  (see 


FIG.  5. 

(Fig.  5).  As  it  begins  to  soften  the  flame  takes  on  a 
golden  glow.  Continue  heating  until  it  is  quite  soft, 
then  take  it  out  of  the  flame,  hold  it  horizontal,  and  let 
one  end  drop  by  its  own  weight,  merely  steadying  it  with 
the  hand,  until  it  has  bent  into  the  angle  desired,  then 
hold  it  steady  for  a  moment  until  it  hardens  in  that  shape. 


PRACTICAL  MANUAL  147 

To  bore  corks.  First  soften  the  cork  until  it  gives  a 
little  when  pinched  between  finger  and  thumb.  This 
can  be  done  by  rolling  the  cork  on  the  floor  under  the 
ball  of  the  foot.  Select  a  cork-borer  a  shade  smaller  than 
the  tube  for  which  the  cork  is  being  bored.  Place  the 
cork  against  a  perpendicular  surface  and  cut  half  way 
through  it  with  a  screwing  motion  of  the  cork-borer, 
being  careful  to  make  the  hole  exactly  in  the  centre,  and 
to  keep  the  borer  at  right  angles  to  the  cork  while  cutting. 
Then  invert  the  cork  and  cut  through  from  the  other  end 
until  the  two  cuts  meet  in  the  middle  of  the  cork.  The 
core  will  come  out  with  the  borer  and  the  edges  of  the  hole 
can  be  smoothed  by  running  the  borer  through  again, 
first  from  one  end  and  then  from  the  other.  A  well- 
bored  cork  should  have  a  perfectly  smooth  cut  and  fit 
tightly  on  the  tube,  though  not  so  tightly  that  excessive 
effort  is  required  to  get  the  tube  through.  Rubber 
stoppers  may  be  bored  in  the  same  way,  but  the  borer 
should  be  kept  wet  with  either  alcohol  or  sodium 
hydroxide. 

In  putting  rubber  tubing  or  stoppers  on  glass  always 
wet  them  a  little.  This  will  make  the  glass  slip  through 
much  more  easily. 

In  fitting  a  bent  tube  into  a  stopper  always  hold  it 
between  the  stopper  and  the  bend,  never  beyond  the 
bend,  otherwise  it  is  liable  to  break  and  cut  the  hand 
badly.  Also,  a  glass  tube  should  always  be  held  as  near 
as  possible  to  the  point  where  force  is  applied;  that  is  to 
say,  in  the  case  where  a  tube  is  being  forced  into  a 
stopper,  always  hold  it  near  the  stopper.  This  reduces 
the  leverage,  and  hence  lessens  the  danger  of  breaking. 
On  the  other  hand,  when  trying  to  break  glass,  as  in 
cutting  tubing,  the  extra  leverage  aids  in  the  breaking, 
and  therefore  the  thumbs  are  placed  some  little  distance 
apart  on  either  side  of  the  cut. 


148  CHEMISTRY  FOR  NURSES  AND  STUDENTS 


LABORATORY  EXERCISES 

1.  To  Make  a  Wash  Bottle. — A  wash-bottle  is  a  flat- 
bottomed  flask  (Florence  flask)  fitted  with  a  two-holed 
rubber  stopper,  through  which  pass  two  tubes.  One 
of  these,  the  mouth-piece,  is  between  three  and  four 
inches  long,  bent  in  the  middle  in  an  obtuse  angle. 
The  other,  the  delivery  tube,  is  about  twelve  inches 
long,  and  is  bent  into  an  acute  angle  about  an  inch  from 
one  end,  this  same  end  being  connected  by  rubber  tubing 
to  a  short  tip  drawn  out  into  a  fine  jet.  The  longer  end 
goes  through  the  stopper  and  reaches  almost 
to  the  bottom  of  the  flask.  It  is  an  im- 
provement if,  after  this  tube  has  been  put 
into  the  stopper,  a  slight  curve  is  made  in 
it  at  the  lower  end  in  the  same  direction  as 
the  upper  bend.  (Fig.  6).  If  the  wash- 
bottle  is  partly  filled  with  water  and  the 
FIG  6  stopper  fitted  in  place  it  will  be  found  that 
by  blowing  gently  through  the  mouth-piece 
a  fine  jet  of  water  is  delivered  through  the  tip,  and  as  this 
tip  is  flexible,  owing  to  the  rubber  connection,  the  stream 
can  be  directed  to  any  desired  spot.  This  arrangement 
is  very  convenient  for  washing  precipitates  in  a  filter, 
and  if  a  wash  bottle  full  of  water  is  always  on  the  desk 
it  saves  many  steps  to  the  sink. 

To  construct.  Draw  roughly  on  a  piece  of  paper 
the  angles  into  which  you  wish  to  bend  your  glass.  Take 
a  glass  tube  and  soften  it  in  the  flame  about  two  inches 
from  one  end.  When  soft  hold  it  a  little  above  the  guide 
on  the  paper  and  bend  it  gently  into  the  same  angle. 
Let  it  cool,  and  cut  it  off  a  little  more  than  two  inches 
below  the  bend.  Round  both  ends  in  the  flame.  Bend 
the  other  tube  in  the  same  way.  To  make  the  tip, 


PRACTICAL  MANUAL  149 

heat  a  piece  of  tubing  in  the  middle  until  it  is  quite  soft, 
then  take  it  out  of  the  flame  and  draw  the  two  ends 
gently  apart,  not  too  quickly.  After  it  has  cooled,  cut 
it  where  it  has  been  drawn  out.  Cut  off  the  end  to  the 
proper  length  and  round  it  in  the  flame.  When  cool 
attach  it  to  the  long  bent  tube  by  an  inch  and  a  half  of 
rubber  tubing. 

2.  To  Estimate   Capacity. — The  ordinary  test   tube 
holds  25  c.c.     Divide  it  as  accurately  as  you  can  into 
five  equal  parts,  making  an  ink  mark  to  indicate  the 
divisions.     Test  the  accuracy  of  your  eye  by  measuring 
5,  10,  15,  and  20  c.c.  into  it  from  the  laboratory  gradu- 
ate.    Correct  your  divisions  if  necessary,  let  the  ink  dry, 
and  brush  over  each  mark  lightly  with  melted  paraffin. 
Keep  this  tube  for  measuring.     In  the  same  way  gradu- 
ate a  beaker  to  hold  50,  100,  and  200  c.c.     In  the  course 
of  your  work  train  your  eye  to  estimate  quantities  ac- 
curately. 

3.  Formation  of  Compounds  from  Elements. — Make 
a  short  coil  of  copper  wire  by  winding  about  two  inches 
of  wire  around  a  pencil.     Put  it  in  a  test  tube  with  a 
pinch  of  powdered  sulphur  and  heat  the  two  together, 
gently  at  first  and  then  more  strongly.     When  the  mix- 
ture is  red  hot  take  the  test  tube  from  the  flame  and 
notice  that  the  glow  increases  for  a  moment  or  two  al- 
though the  test  tube  is  being  cooled.     This  glow  is  due 
to  the  chemical  energy  which  is  set  free  in  the  form  of 
heat  when  the  two  elements,  iron  and  sulphur,  combine. 
(See  p.  16.)     After  the  test  tube  is  cold  break  it  and 
examine  the  contents,  comparing  with  the  original  mix- 
ture.    How  many  indications  can  you  find  to  show  that 
a  new  substance  has  been  produced?     Is  there  any  un- 
changed iron  or  sulphur  left?     Why?     How  could  this 
be  prevented? 


150 


CHEMISTRY  FOR  NURSES  AND  STUDENTS 


Requires:    Copper  wire. 

Powdered  sulphur  (Flowers  of  sulphur). 
Test  tube. 

4.  Decomposition  of  a  Compound  into  its  Elements. 
Take  about  as  much  mercury  rust  (red  oxide  of  mercury) 
as  would  go  on  a  five-cent  piece,  and  put  it  in  a  hard 
glass  test  tube.  Clamp  this  tube  horizontally  in  a  stand 
(See  Fig.  7)  and  heat,  gently  at  first  and  then  strongly. 
At  intervals  thrust  a  glowing  (not  burning)  splinter  into 
the  tube.  What  evidences  are  there  of  change  taking 
place?  Is  the  gas  ("air")  in  the  tube 
the  same  at  the  beginning  and  at 
the  end  of  the  experiment?  Where 
might  the  new  gas  have  come  from? 
By  what  properties  would  you  de- 
scribe it?  The  name  of  this  gas  is 
ox}rgen.  After  heating  for  five 
minutes  allow  the  tube  to  cool,  empty 
.the  contents  on  to  a  piece  of  paper 
and  examine  them.  The  silvery 
liquid  is  mercury.  Where  has  it 
come  from  ?  Of  what  elements  is  mercury  rust  made  up  ? 
The  residues  should  be  put  into  a  stock  bottle  and 
saved,  as  mercury  and  all  its  compounds  are  valuable. 

Requires:     Mercuric  oxide. 

Hard  glass  test  tube. 
Stand  and  clamp. 
Splinters  of  soft  wood. 

6.  Separation  of  a  Mixture  into  its  Components  by 
Filtration. — Mix  thoroughly  about  a  teaspoonful  each 
of  salt  and  sand  in  a  beaker.  Heat  a  little  of  it  in  a 
test  tube  as  you  did  the  iron  and  sulphur.  Is  there  any 
evidence  of  change  taking  place  in  this  case?  To  the 
rest  of  the  mixture  add  50  c.c.  of  water  and  stir  thorough- 
ly. What  happens  to  the  salt?  Would  this  action  be 


FIG.  7. 


PRACTICAL  MANUAL 


151 


hastened  or  increased  by  heating  the  water?  Why? 
(See  p.  27.)  What  is  the  general  method  for  getting 
a  substance  into  solution  as  fast  as  possible?  When  the 
salt  is  all  dissolved,  fit  a  filter  paper  into  a  funnel  which 
is  supported  in  a  stand.  (See  Fig.  8).  Pour  the  clear 
solution  carefully  through  the  filter,  using  a  glass  rod  to 
guide  the  stream  of  water  and  being  careful  not  to  let 
it  flow  over  the  edge  of  the  paper.  Collect  the  portion 
that  comes  through  (the  filtrate)  in  an  evaporating  dish, 
and  evaporate  it  to  less  than  half  its  bulk.  This  is  most 


Fio.  8. 

quickly  done  by  supporting  the  dish  on  a  wire  gauze 
over  a  burner  and  heating  it,  first  to  boiling  and  then, 
as  it  becomes  more  concentrated,  just  short  of  boiling. 
As  the  solution  becomes  concentrated  it  tends  to  spatter. 
The  evaporation  may  be  stopped  at  this  point  and  the 
solution  allowed  to  cool.  It  is  sometimes  more  conve- 
nient to  leave  a  solution  to  evaporate  slowly  by  itself  at 
room  temperature.  Jn  such  a  case  it  should  be  protected 
from  dust  by  covering  it  with  a  paper  cone  or  an  inverted 
beaker  which  is  tipped  a  little  to  allow  of  free  circulation 


152  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

of  air.  On  standing,  white  crystals  separate  from  the 
liquid.  Dry  a  few  of  these  with  filter  paper,  grind  them 
to  powder  and  compare  with  the  original  salt.  How 
many  properties  have  they  in  common  ? 

While  the  salt  solution  is  evaporating  add  another 
50  c.c.  of  water  to  the  sand,  stir  well,  allow  to  settle, 
and  pour  away  the  clear  liquid.  This  is  known  as 
"washing  by  decantation. "  Repeat  this  once  more, 
and  then  transfer  the  sand  to  the  filter.  This  can  be 
most  readily  accomplished  by  washing  it  out  of  the 
beaker  and  into  the  funnel  with  a  stream  of  water  from 
the  wash-bottle.  Wash  the  sand  in  the  funnel  by  pouring 
water  over  it  until  the  water  coming  through  has  no 
longer  a  salty  taste. 

In  this  experiment  the  mixture  of  salt  and  sand  has 
been  separated  into  its  component  parts  by  taking 
advantage  of  the  fact  that  one  component  is  soluble 
while  the  other  is  entirely  insoluble.  Mixtures  of  two 
soluble  or  two  insoluble  components  can  rarely  be  sepa- 
rated by  mechanical  means. 

Requires:    Salt. 
Sand. 
Beaker. 

Funnel  and  stand. 
Filter  paper. 
Glass  rod. 
Evaporating  dish. 
Wash  bottle. 

6.  Distillation.  (Demonstration) . — Arrange  apparatus 
as  shown  in  sketch  (Fig.  9).  In  the  flask  put  water 
colored  with  ink  or  a  dye.  On  boiling  the  water  distils 
over  colorless.  If  a  centigrade  thermometer  is  inserted 
in  the  cork  of  the  distilling  flask  so  that  the  bulb  of  the 
thermometer  is  just  below  the  outlet  tube  of  the  flask,  the 
temperature  of  the  boiling  vapor  may  be  noted.  If  this 


PRACTICAL  MANUAL 


153 


cork  is  replaced  by  "another  carrying  a  Fahrenheit 
thermometer  the  boiling  point  of  water  on  the  two  scales 
may  be  compared,  and  a  similar  comparison  of  the  freez- 
ing points  may  be  made  by  placing  the  two  thermometers 
in  a  beaker  of  ice  and  water  for  a  short  time. 


Requires: 


Condenser. 

500  c.c.  distilling  flask. 

Beaker. 

Thermometers  (Centigrade  and  Fahrenheit  scales.) 

Clamp  and  stand. 

Tripod  or  stand  for  flask. 


Wafer 


FIG.  9. 

7.  Decolorization  of  a  Liquid  by  Animal  Charcoal. 
(Demonstration). — In  a  500  c.c.  flask  put  300  c.c.  of 
water  colored  with  a  little  red  ink.  Add  a  handful  of 
powdered  animal  charcoal,  stopper  the  flask,  and  shake 
well  for  a  few  minutes.  On  filtering,  the  liquid  will  be 
found  to  be  colorless. 

Requires:     Powdered  animal  charcoal. 
500  c.c.  flask. 
Filter  paper. 
Beaker. 
Funnel  and  stand. 


154  CHEMISTRY  FOE  NURSES  AND  STUDENTS 

8.  Oxidation.     Gain  in  Weight  when  Substances  are 
Oxidized.     (Demonstration). — Heat  a  porcelain  crucible 
and  its  lid  with  a  low  flame  to  dry  them  thoroughly, 
cool,  and  weigh  to  the  nearest  hundredth  of  a  gram. 
Polish  a  piece  of  magnesium  ribbon  and  fold  it  back  and 
forth  on  itself  without  breaking  so  that  it  occupies  as 
small  compass  as  possible,  but  not  so  tightly  that  the 
ah-  cannot  circulate  freely  through  the  folds.     Nearly 
fill  the  crucible  with  the  folded  magnesium,  taking  care 
that  it  does  not  project  above  the  edge  of  the  crucible 
at  any  point.     Cover  the  crucible  with  the  lid,  leaving 
just  a  crack  open,  and  heat  it  on  a  pipe-clay  triangle. 
At  frequent  intervals  lift  the  lid  cautiously  with  a  pair 
of  clean  forceps.     If  smoke  escapes  replace  the  lid  at 
once.     Should  there  be  no  sign  of  reaction  increase  the 
heat.     Finally,   when  all  the  magnesium  has  lost  its 
metallic  lustre  and  been  transformed  into  the  grayish 
oxide,  take  the  lid  off  altogether  and  heat  very  hot  for 
about  five  minutes.     Cool  and  weigh. 

Requires:     Magnesium  ribbon. 
Porcelain  crucible. 
Balance  and  weights. 
Pipe-clay  triangle  and  stand. 

9.  Production  of  Oxygen  by  Green  Plants  in  Sunlight. 

(Demonstration).  Pass  carbon  dioxide  through  a  liter 
or  more  of  water  for  twenty  minutes  generating  carbon 
dioxide  for  the  purpose  as  follows. 

In  a  500  c.c.  flask  put  a  few  marble  chips  or  fragments 
of  chalk.  Fit  the  flask  with  a  two-holed  stopper,  through 
one  hole  of  which  a  thistle  tube  passes  down  to  the  bottom 
of  the  flask,  while  the  other  is  fitted  with  a  glass  tube 
bent  at  right  angles.  Connect  this  with  rubber  tubing 
to  another  right  angled  tube  passing  through  a  stopper 
and  down  to  the  bottom  of  a  second  flask  containing 


PRACTICAL  MANUAL 


155 


100  c.c.  of  water.  Through  a  second  hole  in  the  stopper  of 
this  flask  passes  a  short  right-angled  tube  which  reaches 
just  below  the  stopper,  and  which  is  connected  in  its 
turn  with  a  straight  tube  passing  into  a  large  jar  (bat- 
tery jar)  of  water  (see  Fig.  10).  On  pouring  dilute 


FIG.  10. 

(1.5)  hydrochloric  acid  through  the  thistle  tube  a  stream 
of  carbon  dioxide  is  generated.  When  the  action  ceases 
add  more  acid,  or  more  marble  if  necessary. 

When  the  water  is  saturated,  take  as  many  sprays 
of  elodea  or  myriophyllum  (the  plants  commonly  used 
for  gold  fish  bowls)  as  will  fit  into  a 
large  (200  X  25  mm.)  test  tube  with- 
out crushing.    Tie  them  loosely  together 
and  put  them  in  the  carbonated  water, 
clipping  their  stems  after  they  are  under 
water.     Put  the  test  tube  in  the  jar, 
let  it  fill  with  water,  and  invert  it  with 
its   mouth   under   the   surface   of   the 
water,  so  that  the  tube  remains  full  of 
water.       Clamp  it  upright,   with  the 
mouth  just  under  the  surface,  slip  the 
elodea  up  into  the  test    tube,  and  place  the  whole  in 
bright  sunlight  (see  Fig.  11).     The  plant  absorbs  carbon 
dioxide  from  the  water  and  uses  it  as  food,  giving  off 
oxygen  as  a  product  of  metabolism. 


FIG.  11. 


156  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

When  a  sufficient  amount  of  gas  has  collected  remove 
the  elodea  and  test  the  gas  with  a  glowing  splinter. 
The  experiment  should  not  be  left  running  for  more 
than  two  hours,  as  by  the  end  of  that  time  the  amount  of 
carbon  dioxide  given  off  in  respiration  will  tend  to  exceed 
the  amount  of  oxygen  produced  by  photosynthesis, 
and  a  test  for  oxygen  cannot  be  obtained.  If  it  is 
impossible  to  finish  the  experiment  and  make  the  test 
during  one  class  period  the  gas  can  be  kept  standing  over 
water  until  next  period,  provided  the  elodea  is  removed. 

Requires:    Two  flasks  with  two-holed  stoppers,  right-angled  glass 

tubes,  and  rubber  connections. 
Thistle  tube. 
Battery  jar. 

Large  test  tube  (200  X  25  mm.). 
Stand  and  clamp. 
Elodea  or  myriophyllum. 

10.  Solution. — Measure  50  c.c.  of  water  in  a  beaker, 
add  a  small  lump  of  sodium  carbonate  and  note  the 
rate  at  which  it  dissolves.  Grind  an  equal  amount  of 
sodium  carbonate  to  a  fine  powder  and  add  it  to  the  same 
solution.  Compare  the  rate  of  solution  of  the  powdered 
substance.  Continue  to  add  powdered  sodium  car- 
bonate, a  spoonful  at  a  time,  with  constant  stirring, 
until  no  more  will  dissolve.  Then  heat  the  water  to 
boiling  and  continue  to  add  sodium  carbonate  until 
no  more  will  dissolve  at  that  temperature.  What  effect 
has  temperature  on  the  solubility  of  sodium  carbonate 
in  water?  Allow  the  solution  to  cool.  Explain  what 
happens. 

To  prepare  lime-water.  Lime  water  is  a  saturated 
solution  of  calcium  hydroxide,  but  is  best  prepared  by 
starting  with  quicklime,  calcium  oxide. 

To  3  gms.  of  quicklime  add  gradually  100  c.c.  of  water. 
Let  it  stand,  with  occasional  stirring,  for  half  an  hour. 


PRACTICAL  MANUAL  157 

Allow  the  suspended  parts  to  settle,  decant  off  the  clear 
liquid  and  discard  it.  Add  to  the  residue,  which  is 
calcium  hydroxide  (see  p.  39),  1000  c.c.  of  water,  stir 
thoroughly,  leave  standing  for  twenty-four  hours,  stir 
thoroughly  once  more,  let  the  coarser  particles  settle, 
and  pour  the  suspension  of  fine  powder  ("milk  of  lime") 
into  a  well  corked  bottle.  The  solid  will  settle  slowly, 
leaving  the  clear  saturated  solution  on  top. 

Requires:     Sodium  carbonate. 
Quicklime. 
Beakers. 
"Gem  jars,"  quart  size,  for  preparing  limewater. 

'II.  Osmosis.  (Demonstration). — Fill  a  test  tube  with 
a  dilute  solution  of  copper  sulphate  and  introduce 
into  this  a  drop  or  two  of  a  concentrated  solution  of 
potassium  ferrocyanide  by  letting  it  run  in  from  a 
dropping  tube  (or  medicine  dropper)  of  which  the  mouth 
is  just  under  the  surface  of  the  copper  sulphate.  As  the 
drop  comes  in  contact  with  the  copper  sulphate  in- 
soluble copper  ferrocyanide  is  precipitated  at  the  bound- 
ary of  the  two  solutions,  forming  a  semi-permeable 
membrane  which  surrounds  the  drop.  Since  the  solu- 
tion outside  the  little  cell  thus  formed  is  more  dilute 
than  that  inside  water  will  tend  to  pass  in  and  the  drop 
will  be  seen  to  swell  gradually,  until  finally,  in  the  course 
of  half  an  hour  or  so,  the  pressure  becomes  so  great 
that  the  skin  bursts.  By  reversing  this  experiment 
and  adding  a  drop  of  dilute  copper  sulphate  to  a  test 
tube  of  the  more  concentrated  potassium  ferrocyanide 
we  get  an  illustration  of  plasmolysis.  The  water  passes 
out  from  the  drop  of  dilute  solution  causing  a  shrinking 
and  wrinkling  of  the  surrounding  membrane. 

Requires:     Test  tube. 

Glass  dropping  tube. 

Solution  of  copper  sulphate  (7  gms.  to  100  c.c.). 

Solution  of  potassium  ferrocyanide  (20  gms.  in  100  c.c.). 


158 


CHEMISTRY  FOR  NURSES  AND  STUDENTS 


12.  Study  of  Carbon  Dioxide. — Preparation  from 
carbonates.  To  a  pinch  of  sodium  carbonate  in  a  test 
tube  add  a  little  dilute  hyrochloric  acid.  Repeat  with 
sodium  acid  carbonate,  calcium  carbonate  (marble),  and 
baking  powder. 

Set  up  an  apparatus  like  sketch  (Fig.  12),  consisting 
of  a  test  tube  fitted  with  a  cork  through  which  passes 
a  tube  about  four  inches  long  with  a  right-angled  bend 
in  the  middle.  Connect  this  by  about  four  inches  of 
rubber  tubing  to  a  straight  tube  passing  down  to  the 
bottom  of  another  test  tube  (without  a 
cork).  In  this  second  tube  put  five  c.c. 
of  clear  lime  water,  and  in  the  first  tube 
put  about  half  a  teaspoonful  of  sodium 
carbonate.  Add  a  little  dilute  hydro- 
chloric acid  and  quickly  replace  the  cork. 
Note  what  happens  to  the  lime  water. 
FIG.  12.  This  is  a  test  for  the  gas  carbon  dioxide. 

(Seep.  21.) 

Breathe  through  clear  lime  water  by  blowing  through 
a  glass  tube.  Explain  what  happens. 

Pour  a  little  clear  lime  water  into  a  beaker  and  leave 
open  to  the  air  for  half  an  hour  or  more.  Explain  what 
happens. 

Use  the  same  apparatus  as  above,  but  without  the 
lime  water.  Instead  of  sodium  carbonate  use  fragments 
of  marble  or  chalk,  and  add  dilute  acid  as  before.  Hold 
a  burning  match  at  the  end  of  the  outlet  tube.  Direct 
the  outlet  tube  towards  the  wick  of  a  lighted  candle. 
Explain  what  happens. 

Solubility  of  carbon  dioxide.  Allow  carbon  dioxide 
to  pass  into  water  in  a  test  tube,  using  the  same  appara- 
tus as  above.  After  a  few  moments  test  the  water  with 
clear  lime  water.  Explain  the  result. 


PRACTICAL  MANUAL  159 

Requires:    Sodium  carbonate. 

Sodium  acid  carbonate. 

Baking  powder. 

Marble,  or  chalk. 

Dilute  hydrochloric  acid  (1.5). 

Lime  water. 

Test  tubes. 

Glass  tubes  and  rubber  connections. 

13.  Study  of  acids. — In  each  of  four  test  tubes  put 
5  c.c.  of  water,  and  add  to  one  a  couple  of  drops  of  hydro- 
chloric acid,  and  to  the  others  an  equal  amount  of  sul- 
phuric,  nitric,    and   acetic   acids  respectively.     Dip   a 
glass  rod  in  the  solutions  and  taste  each  one.     Put  a 
drop  of  each  on  a  piece  of  blue  litmus.     To  each  solution 
add  a  few  iron  filings  or  tacks.     (Any  other  metal,  ex- 
cept copper,  would  have  the  same  action).     Test  the 
gas  given  off  with  a  flaming  splinter.     Note  carefully 
what  happens  both  to  the  gas  and  to  the  splinter.     This 
is  a  characteristic  test  for  hydrogen. 

Requires:    Acids  (Hydrochloric,  sulphuric,  nitric,  and  acetic). 
Litmus  (blue). 
Iron  filings  or  tacks. 
Test  tubes. 
Splinter. 

14.  Study  of  Bases. — Take  small  fragments  of  sodium 
hydroxide,  potassium  hydroxide,  and  sodium  carbonate, 
and  dissolve  each  one  separately  in  about  5  c.c.  of  water 
in  a  test  tube.     Note  the  taste  and  feeling  of  the  solu- 
tions and  their  action  on  red  litmus  paper.     Do  these 
three  substances  all  belong  to  the  same  class?     What  is 
the  distinction  between  them?     (See  p.  39). 

Requires:    Sodium  and  potassium  hydroxides. 
Sodium  carbonate. 
Litmus  (red). 
Test  tubes. 


160  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

15.  Neutralization. — To  5  c.c.   10  per  cent,  sodium 
hydroxide  solution  in  a  beaker  add  about  3  c.c.  of  dilute 
(1.5)  hydrochloric  acid,  then  continue  to  add  acid,  drop 
by  drop,  stirring  after  each  addition  and  testing  with 
litmus  paper.     In  making  these  tests  put  the  litmus 
paper  on  a  clean  glass  surface  (the  bottom  of  an  inverted 
beaker  will  do),  take  a  small  drop  on  a  glass  rod  and 
touch  it  to  a  fresh  spot  on  the  paper.     When  the  solu- 
tion no  longer  affects  red  litmus,  test  it  with  blue.     At 
neutralization  point  neither  red  nor  blue  litmus  is  affect- 
ed.    Why? 

Requires:     Sodium  hydroxide  (10  per  cent.). 
Hydrochloric  acid  (1.5). 
Red  and  blue  litmus  paper. 
Beaker. 
Dropping  tube  and  stirring  rod. 

16.  Catalysts    and    Enzymes.     (Demonstration). — (a) 
Manganese   Dioxide   as   a   Catalyst. — Heat   5   c.c.    of 

hydrogen  peroxide  in  a  test  tube  and  test  the  gas  evolved 
with  a  glowing  splinter. 

To  another  5  c.c.  of  hydrogen  peroxide  at  room  tem- 
perature add  a  pinch  of  manganese  dioxide  and  test  the 
gas  as  before. 

This  is  an  example  of  a  catalyst  bringing  about  a 
reaction  at  room  temperature  which  would  otherwise 
require  heat. 

Requires:  Hydrogen  peroxide. 
Manganese  dioxide. 
Test  tube  and  splinter. 

(6)  Action  of  the  Enzyme  of  Liver  on  Fats. — An  extract 
of  liver  is  made  by  putting  a  piece  of  liver  about  three 
inches  square  through  the  meat  chopper  and  then 
grinding  it  in  a  mortar  with  a  handful  of  sand  and  a  little 
water  until  it  is  reduced  to  a  fine  pulp,  the  finer  the  better. 


PRACTICAL  MANUAL  161 

Add  150  c.c.  of  water,  stir  thoroughly  for  a  few  minutes, 
and  filter  through  cheese-cloth. 

Melt  a  bit  of  butter  the  size  of  a  small  bean,  and  put  it 
in  a  test  tube  with  5  c.c.  of  the  liver  extract,  shaking  the 
two  together  until  the  fafc  is  emulsified.  Put  a  cotton 
plug  in  the  tube  and  leave  it  in  the  incubator  (or  in  a 
warm  place)  at  a  temperature  of  not  over  30°C.  for  thirty- 
six  hours.  Note  the  strong  unpleasant  odor  of  butyric 
acid,  due  to  the  hydrolysis  of  the  fat.  For  comparison 
carry  out  an  exactly  similar  experiment,  using  liver 
extract  which  has  been  boiled  for  a  minute.  To  what  is 
the  difference  due? 

(c)  Precipitation  of  an  enzyme. — To  25  c.c.  of  liver 
extract  add  double  its  volume  of  95  per  cent,  alcohol. 
The  enzymes  are  precipitated  (see  p.  51),  along  with 
much  protein  material  from  the  liver.  Filter  the  mass, 
discarding  the  filtrate,  and  pour  25  c.c.  of  water  through 
the  filter,  collecting  it  in  a  small  beaker.  To  this  add 
triple  its  volume  of  alcohol  and  a  few  drops  of  strong 
salt  solution.  On  standing  the  enzyme  is  reprecipitated, 
this  time  without  so  much  protein  contamination. 

Requires:    Liver  extract. 
Butter. 

95  per  cent,  alcohol. 
Strong  sodium  chloride  solution. 
Test  tubes  and  small  beakers. 
Filter  paper,  funnel,  and  stand- 

17.  Experiments  on  Fats. — Test  the  solubility  of  the 
fat  in  water.  In  alcohol.  In  ether.  What  are  your 
conclusions? 

Shake  up  a  drop  of  olive  or  cod-liver  oil  with  3  c.c.  of 
water.  Does  it  form  an  emulsion?  Repeat,  using 
soapy  water.  Result?  Repeat  using  sodium  carbonate. 
Result?  (See  p.  29.) 

Test  for  glycerine  in  fat.     Mix  a  drop  of  glycerine 

11 


162  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

with  a  little  powdered  potassium  acid  sulphate  in  a  dry 
test  tube  and  heat.  Note  the  odor  cautiously.  Repeat, 
using  a  fat  instead  of  pure  glycerine. 

Requires:    Fat  or  oil. 

Sodium  carbonate  solution. 

Glycerine. 

Potassium  acid  sulphate. 

Test  tubes. 

18.  Preparation  of  Soap. — Melt  about  a  tablespoonful 
of  fat  in  an  evaporating  dish,  stirring  constantly  while 
heating.  When  melted,  add  gradually  about  25  c.c.  of  10 
per  cent,  sodium  hydroxide,  beating  it  into  the  fat  to  pre- 
vent burning.  What  reaction  takes  place?  (See  p.  91). 
Then  add  50  c.c.  of  a  strong  solution  of  common  salt,  mix, 
and  leave  to  cool.  When  cold  lift  out  the  cake  of  soap, 
wash  well  with  cold  water,  melt  it  with  20  c.c.  of  water, 
mixing  well,  and  cool  again.  What  is  soap? 

Dissolve  a  little  soap  in  pure  (distilled)  water.  In 
hard  water.  (Water  not  hard  may  be  made  so  by  adding 
a  few  drops  of  lime  water  to  it.)  Explain  the  difference. 

To  a  little  soap  solution  add  a  few  drops  of  hydro- 
chloric acid.  What  is  the  precipitate? 

Requires:     Fat. 

Sodium  hydroxide  (10  per  cent.). 
Strong  sodium  chloride  solution. 
Evaporating  dish. 
Hydrocholoric  acid. 

10.  Experiments  on  Carbohydrates. — (a)  Tests  for 
Constituents.  Heat  a  little  sugar  in  a  test  tube  and  note 
the  water  given  off  as  the  sugar  darkens.  On  strong 
heating  all  the  hydrogen  and  oxygen  are  given  off  in  the 
form  of  water  and  a  black  mass  of  carbon  is  left 

Requires:     Cane  sugar. 
Test  tube. 


PRACTICAL  MANUAL  163 

(b)  Fehling   Solution    Test  for  Glucose.     (See  p.  98.) 
Mix  about  3  c.c.  each  of  the  blue  and  the  colorless  parts  of 
the  Fehling  solution  and  add  a  few  drops  of  a  solution  of 
glucose.     Heat  the  tube  gently  and  note  the  change  of 
color.     To  what  is  it  due?     Repeat  with  cane  sugar 
solution. 

To  3  c.c.  of  cane  sugar  solution  add  3  drops  of  hydro- 
chloric acid  (1.5)  and  boil  for  two  minutes.  Neutralize 
the  acid  with  a  drop  or  two  of  sodium  hydroxide,  and 
test  the  solution  with  Fehling  solution  as  before.  Ex- 
plain. 

Requires:     Glucose. 

Fehling  solution.1  • 

Hydrochloric  acid  (1.5). 
Sodium  hydroxide  (10  per  cent.). 
Test  tubes. 

(c)  Tests  with  Starch.     Test  the  solubility  of  starch 
in  cold  water.     In  boiling  water.     Make  a  little  "  starch 
paste"  by  mixing  a  teaspoonful  of  starch  with  200  c.c. 
of  cold  water  and  boiling  for  three  minutes.     Test  a 
little  of  this  starch  paste  with  iodine  solution.     With 
Fehling  solution.     To  1  c.c.  add  two  drops  of  hydro- 
chloric acid  and  boil  for  three  minutes.     Test  again 
with  Fehling  solution. 

To  1  c.c.  of  the  unaltered  starch  paste  add  3  c.c.  of 
saliva.  Put  the  tube  in  a  beaker  of  water  at  a  tempera- 
ture of  not  more  than  30°C.  for  five  minutes.  Test 
with  Fehling  solution. 

Crumble  a  bit  of  plain  unsweetened  cracker  (soda 
cracker)  in  water  and  test  with  Fehling  solution.  What 

1  Fehling  solution  is  prepared  as  follows.  (Benedict's  modification). 
Dissolve  34.65  gms.  of  copper  sulphate  in  water  and  make  up  to  500  cc. 
Dissolve  100  gms.  of  anhydrous  sodium  carbonate  and  175  gms.  of 
Rochelle  salt  in  water  and  make  up  to  500  cc.  Keep  these  two  solutions 
separately  in  rubber-stoppered  bottles  and  mix  in  equal  volumes  when 
needed. 


164  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

is  the  chief  food  constituent  of  bread,  crackers,  etc.? 
Chew  a  bit  of  cracker  well  for  at  least  a  minute  and  test 
with  Fehling  solution.  What  has  happened?  To  what 
is  it  due? 

Action  of  diastase  with  starch.  To  the  remainder  of 
the  starch-  solution  add  a  diastase  capsule  and  keep  in 
warm  water  at  as  nearly  50°C.  as  possible.  It  must 
not  be  allowed  to  warm  up  above  65°.  At  intervals  of 
five  minutes  test  a  few  drops  with  iodine  solution. 
When  the  iodine  no  longer  shows  starch  present,  test 
with  Fehling  solution.  What  has  taken  place,  and  to 
what  is  it  due? 

Requires:    Diastase  capsules. 
Starch. 

Fehling  solution. 

Iodine  solution.     (Iodine  crystals  dissolved  in  a  dilute 
solution  of  potassium  iodide.) 

(d)  Fermentation. — Mix  5  c.c.  of  concentrated  glucose 
solution  ("corn  syrup "  is  very  satisfactory)  in  a  test 
tube  with  quarter  of  a  yeast  cake  made  into  a  paste  with 
5  c.c.  of  water.  Close  the  test  tube  by  means  of  a  cork 
with  a  right-angled  delivery  tube,  connected  by  rubber 
with  another  tube  dipping  below  the  surface  of  a  little 
clear  lime  water  in  a  second  test  tube  which  is  protected 
from  the  air  by  a  cotton  plug.  (See  Fig.  12.)  Leave 
standing  until  next  exercise. 

At  the  next  period  note  the  appearance  of  the  lime 
water.  What  does  this  indicate?  Note  the  alcoholic 
odor  of  the  fermenting  liquid.  Filter  the  liquid,  add 
two  or  three  small  crystals  of  iodine,  and  warm  gently 
for  a  few  moments.  Cool,  and  add  sodium  hydroxide 
until  the  color  of  the  iodine  disappears.  On  standing, 
yellow  crystals  of  iodoform  are  deposited  and  may  be 
recognized  by  their  characteristic  odor.  The  formation 


PRACTICAL  MANUAL  165 

of  iodoform  is  a  test  for  the  presence  of  ethyl  alcohol. 

(See  p.  80.) 

Requires:     Glucose. 
Yeast. 
Lime  water. 
Iodine  crystals. 
Sodium  hydroxide  solution. 
Test  tubes  and  connecting  tubes. 

(e)  Test  for  Sugar  in  Milk. — To  10  c.c.  of  milk  in  a 
beaker  add  an  equal  volume  of  water,  and  warm  gently 
to  between  50°  and  60°C.  Now  add  not  more  than  1  c.c. 
of  5  per  cent,  acetic  acid.  By  this  treatment  the  casein 
of  the  milk  is  precipitated.  Stir  thoroughly,  allow  to 
settle,  decant  the  clear  liquid  through  a  filter  paper, 
and  test  the  filtrate  with  Fehling  solution. 

Requires:     Milk. 

Acetic  acid  (5  per  cent.). 

Fehling  solution. 

Beaker,  funnel,  and  test  tube. 

20.  Tests  on  Proteins. — Put  a  drop  of  strong  nitric 
acid  on  a  little  protein  material.  Note  the  color 
produced. 

Heat  a  little  protein  with  2  or  3  c.c.  of  Millon's  reagent. 
Note  the  color  produced. 

Heat  a  little  protein  with  "biuret  reagent"  in  an 
evaporating  dish.  Note  the  color  change. 

Test  for  the  Constituents  of  Protein,  (a)  Nitrogen. — 
To  a  small  quantity  of  dry  gelatine  add  over  ten  times 
its  amount  of  soda-lime,  and  grind  the  two  together 
in  a  mortar  till  well  pulverized.  Transfer  the  mixture  to 
a  dry  test  tube  and  heat.  Test  the  gas  given  off  with 
red  litmus.  Note  the  pungent  odor  of  ammonia  (a 
little  disguised  by  the  burning  organic  matter). 

(b)  Sulphur. — Mix  about  a  half  teaspoonful  of  dry 
powdered  egg  albumin  with  twice  its  bulk  of  "  fusion 


166 


CHEMISTRY  FOR  NURSES  AND  STUDENTS 


mixture"  in  a  porcelain  crucible.  Set  the  crucible 
on  a  pipe-clay  triangle  (see  Fig.  13)  and  heat  cautiously. 
As  there  is  a  disagreeable  fume  produced  in  this  process 
the  experiment  should  be  carried  on  in  a  draft  cupboard 
or  near  an  open  window  through  which 
the  fumes  can  escape.  As  soon  as  the 
action  begins  in  the  crucible,  take  away 
the  flame  until  it  has  moderated.  Con- 
tinue the  fusion  until  the  product  is  prac- 
tically colorless,  then  allow  the  fused  mass 
to  cool.  Fill  the  crucible  with  water  and 
if  necessary  warm  gently  to  dissolve  the 
fused  material.  Pour  the  solution  into  a 
small  beaker  and  acidify  with  a  few  drops 
of  hydrochloric  acid.  Transfer  to  a  test 
tube,  filtering  if  not  perfectly  clear,  and 
add  a  little  barium  chloride.  A  white 
precipitate  of  barium  sulphate  indicates 
the  presence  of  sulphur. 
Coagulation.  To  20  c.c.  of  egg  white  add  four  times 
its  bulk  of  water.  Heat,  and  note  temperature  of 
coagulation. 

Requires:    Protein  material.     (Either  coagulated  egg  white  of  the 

casein  of  milk  can  be  used  for  the  color  tests.) 
Gelatine.     Powdered  egg  albumin. 
Powdered  egg  albumin. 
Nitric  acid. 
Millon's  reagent.1 
Biuret  reagent.2 

1  Millon's  reagent  is  prepared  as  follows.     Dissolve  200  gms.  of  mercury 
in  its  own  weight  of  concentrated   nitric   acid  (in   draft  cupboard,  on 
account  of  fumes  given  off).    Treat  the  solution  with  twice  its  volume  of 
water,  allow  to  stand,  and  decant  the  clear  solution  from  the  sediment 
which  forms. 

2  Gies'  biuret  reagent  is  prepared  as  follows.     To  500  c.c.  of  10  per  cent, 
sodium  hydroxide  solution  add  12.5  c.c.  of  3  per  cent,  copper  sulphate 
solution. 


FIG.  13. 


PRACTICAL  MANUAL  167 

Soda  lime. 

Fusion  mixture  (1  part  NaaCOs  and  3  parts  KNO3  pow- 
dered and  mixed  together). 
Hydrochloric  acid. 
Barium  chloride  solution  (112  gms.  per  litre). 

^  21.  Hydrolysis  of  Protein  (Demonstration). — Put  the 
whites  of  three  eggs  in  a  flask  and  heat  in  boiling  water 
until  coagulated.  Add  300  c .  c .  of  water  in  which  has  been 
dissolved  15  c.c.  of  concentrated  sulphuric  acid,  and 
leave  on  a  water  bath  (or  on  a  radiator)  until  the  protein 
material  has  been  decomposed,  leaving  only  a  fluffy 
white  insoluble  residue.  Filter  this  off  and  add  to  the 
filtrate  300  c.c.  of  20  per  cent,  barium  hydroxide.  Then 
add  more  carefully  about  25  c.c.  more,  testing  with 
litmus  after  each  addition  until  neutral.  Should  the 
neutral  point  be  passed  add  a  few  drops  of  5  per  cent, 
acetic  acid  until  the  solution  gives  a  very  faint  acid 
reaction.  Allow  it  to  stand  over  night,  or  until  the 
precipitated  barium  sulphate  has  settled  down  to  the 
bottom  of  the  beaker.  Decant  the  clear  solution  through 
a  filter,  finally  transferring  the  precipitate  to  the  funnel. 
Collect  the  filtrate  in  an  evaporating  dish  and  evaporate 
it  to  half  volume  on  a  wire  gauze,  and  then  on  a  water 
bath  to  about  10  c.c.  To  the  syrupy  residue  after 
evaporation  add  95  per  cent,  alcohol  until  no  more 
precipitate  forms,  stirring  continually.  The  sticky  pre- 
cipitate consists  of  peptones  and  proteoses  (see  p.  112). 
Gather  this  precipitate  together  as  much  as  possible 
on  the  side  of  the  dish,  warm  the  solution  gently,  and 
decant  through  a  dry  filter  paper.  The  filtrate  con- 
tains amino  acids  (tyrosine  and  leucine)  which  will 
separate  in  crystalline  form  if  the  solution  is  allowed  to 
evaporate  slowly. 

Requires:     Egg  white. 

Barium  hydroxide  (20  per  cent,  solution). 


168  CHEMISTRY  FOB  NURSES  AND  STUDENTS 

95  per  cent,  alcohol. 
500  c.c.  flask. 
750  c.c.  beaker. 
Evaporating  dish. 
Funnels  and  stand. 

22.  Experiments  on  Blood.  (Demonstration.) — (a) 
Clotting  of  Blood. — Leave  300  c.c.  of  freshly  drawn  blood 
in  an  open  beaker  until  a  solid  clot  has  formed.  Then 
cover  and  allow  to  stand  for  at  least  twenty-four  hours. 
The  clot  shrinks  and  the  yellowish  serum  separates 
from  it. 

(b)  Defibrination   of  Blood. — Stir   300   c.c.    or   more 
of   freshly   drawn   blood   vigorously   for   five   to   eight 
minutes.     Collect  the  solid  which  separates  and  wash 
it  well  with  water.     This  is  fibrin  (see  p.  131).     Test 
it  for  protein.     The  residue  from  which  the  fibrin  has 
been  removed  is  called  defibrinated  blood. 

(c)  Reactions  of  Haemoglobin. — Take   10  c.c.   of  de- 
fibrinated blood  in  each  of  three  test  tubes.     Shake  one 
well  with  air  so  that  it  can  take  up  as  much  oxygen  as 
possible.     The    haemoglobin    is    converted    into    oxy- 
haemoglobin.     To  the  second  add  a  few  drops  of  Stokes 
reagent.1     This  is  a  strong  reducing  agent  and  reduces 
the    oxyhaemoglobin    present    to    haemoglobin.     Pass 
illuminating  gas  through  the  third  tube.     Illuminating 
gas  contains  carbon  monoxide,  which  unites  with  the 
haemoglobin  (see  p.  133).     Note  the  difference  in  color 
in  the  three  tubes. 

(d)  Laking  of  Blood. — To  a  few  c.c.  of  defibrinated 
blood  add  distilled  water  little  by  little  and  note  the 
effect.     If  a  microscope  is  available  examine  slides  of 
the  blood  before  and  after  laking  (see  p.  134). 

1  Stokes  reagent  is  prepared  as  follows:  Dissolve  3  gms.  of  ferrous 
sulphate  in  25  c.c.  of  cold  water.  Dissolve  2  gms.  of  tartaric  acid  in  the 
same  amount  of  water.  Mix  the  two  solutions  and  add  50  c.c.  water. 
Just  before  using  add  strong  ammonium  hydroxide  until  the  precipitate 
first  formed  just  dissolves. 


PRACTICAL  MANUAL  169 

CHEMICALS  AND  APPARATUS  REQUIRED  FOR  A  CLASS  OP 
TEN  STUDENTS 

(Items  marked  #  are  used  for  demonstration  or  for 
making  up  a  quantity  of  solution,  and  need  not  be  in- 
creased for  a  larger  number  of  students.) 

CHEMICALS 

Amount  Name 

1      Ib.       Acid,  Acetic# 

Hydrochloric# 

Nitric# 

Sulphuric# 

1  liter    Alcohol,  95  per  cent.# 

2  oz.       Animal  charcoal  (powdered)# 
y±  Ib.       Barium  chloride# 

%  Ib.       Barium  hydroxide/ 

2  oz.       Calcium  oxide 

3^  Ib.  Calcium  carbonate  (marble  chips) 

y±  Ib.  Copper  sulphate  (cryst.)# 

3  ft.  Copper  wire  (medium  size) 
15  Diastase  capsules 

H  oz.  Egg  albumin  powdered 

3      gms.  Ferrous  sulphate# 

1      oz.  Gelatine  (powdered,  preferably) 

1      oz.  Glucose  (corn  syrup) 

Y±  oz.  Glycerine 

20      c-c.  Hydrogen  peroxide# 

Y±  Ib.  Iron  filings  or  tacks 

1      oz.  Iodine 

1      roll  Magnesium  ribbon 

1      gm.  Manganese  dioxide,  powdered# 

Y±  Ib.  Mercuric  oxide  (Red  oxide  of  mercury) 

K  Ib.  Mercury# 

1      oz.  Potassium  acid  sulphate 

20      gms.  Potassium  ferrocyanide# 

M  Ib.  Potassium  hydroxide# 

5      gms.  Potassium  iodide 

y±  Ib.  Potassium  nitrate 

K  Ib.  Rochelle  salt  (sodium  potassium  tartrate)# 

1      Ib.  Soda  lime 


170  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

Amount  Name 

100      gms.  Sodium  carbonate  (Anhydrous)# 

2      Ibs.  Sodium  carbonate,  crystalline  (Washing  soda) 

1      oz.  Sodium  bicarbonate 

1      Ib.  Sodium  chloride 

1      Ib.  Sodium  hydroxide 

K  Ib.  Starch 

^  Ib.  Sugar  (cane) 

1  oz.  Sulphur  (Flowers) 

2  gms.  Tartaric  acid# 


PRACTICAL  MANUAL  171 

APPARATUS 

Balance  and  Weights. — For  student  use  the  small  horn  pan  balances 
(Fig.  14)  will  be  found  very  satisfactory.  They  are  sentitive  to  1/100 
of  a  gram.  For  weighing  larger  quantities,  as  in  making  up  solutions 
for  laboratory  use,  the  Harvard  trip  balance  (Fig.  15)  is  more  con- 
venient. Metric  weights  from  centigrams  up  to  200  gms.  will  be 
required. 

Amount         Name 

1  Battery  jar#  (for  exp.  9).     Plain  glass  jar  (Fig.  16). 

Height  8  in.,  diameter  6  in. 

30  Beakers  (Fig.  17).     350  c.c.  capacity 

5  500  c.c.  capacity^ 

2  750  c.c.  capacity^ 

2      doz.  Bottles  #  Y2  pt.  (500  c.c.).     Narrow  mouth. 
J£  6  oz.     Salt  mouth. 

K  4 

1  doz.  Bunsen  burners  (Fig.  18).  Where  acetylene  gas  is  used  a 
special  form  of  burner  is  required.  If  the  laboratory 
is  not  supplied  with  gas,  small  alcohol  lamps  may 
be  used  satisfactorily. 

10  Clamps  and  holders,  small  size    (Fig.  20),  for  exp.  4. 

1  large  (Fig.  21),  for  exp.  6.# 

1  Condenser,  Liebig's,  (Fig.  22)  for  exp.  6.# 

1  set       Cork  borers. 

2  gross    Corks,  No.  6. 

15  Crucibles  and  lids  (Fig.  23).     Capacity  about  12  c.c. 

12  Evaporating  dishes  (Fig.  24).     About  200  c.c.  capacity 

3  1%  liters,  for  making  solutions,  etc.# 
1  pkg.    Filter  paper,  diameter,  5  in. 

1  8  in.# 

18  Flasks,  flat  bottomed  or  Florence 

(Fig.  25)  1000  c.c.  capacity. 

3  500  c.c.  for  exp.9.# 

2  distilling  (Fig.  26)  500  c.c.  for  exp.6.# 
10                 Forceps 

15  Funnels  (Fig.  27)  diameter  3  in. 

3  5  in.# 

10  Fish-tail  or  wing  tops  for  burners  (Fig.  19) 

10  "Gem  jars,"  quart  size,  for  preparation  of  lime  water. 

2  doz.     Glass  rods,  length  5  in. 

1  Ib.       Glass  tubing,  outside  diameter  about  7  mm. 


172  CHEMISTRY  FOR  NURSES  AND  STUDENTS 

Amount          Name 

3  Graduates  100  c.c.# 

2  1000  c.c.# 

12  Wire  gauzes,  5X5  in.     (Nichrome  wire,  although  more 

expensive  in  the  beginning  wears  better  than   the 
cheaper  varieties.) 
2      pkgs.  Litmus  paper,  red. 
2  blue. 

10  Mortars  and  pestles  (Fig.  28)  diameter  10  cms. 

1  16  cms.# 
10                 Pipe-clay  triangles 

10  Ring  stands  (supports),  (Fig.  29).     Small  size,  with  two 

rings. 

2  Large  size,  with  four  rings. # 
1      Ib.        Rubber  stoppers,  two-hole,  no.  6 

6      ft.  Rubber  connection  tubing,  inside  diameter,  %6  in. 

6      ft.  condenser  34  in.# 

24      ft.  burner  Me  m- 

3  Test  tubes  (Fig.  30).     Size  8X1  in.  for  exp.  9.# 
6  doz.  Test  tubes.    Size  6X%  in. 

1  doz.         Test  tubes,  hard  glass,  6X%  in.  for  exp.  4. 

1  Thermometer,  centigrade  scale. # 

1  Fahrenheit.# 

1  Thistle  tube  (Fig.  31). # 

10  Water  baths.     A  water  bath  is  the  chemist's  equivalent 

for  a  double  boiler,  and  is  a  vessel  in  which  water  can 
be  boiled  and  in  which  a  smaller  vessel  can  be  placed. 
For  small  amounts  of  material  two  beakers  serve  very 
well,  the  larger  one  containing  water,  and  the  smaller 
the  substance  to  be  heated.  For  larger  amounts  a 
kitchen  sauce  pan  can  be  used  as  the  outer  vessel. 
The  dealers  supply  copper  rings  which  fit  the  top  of 
the  sauce  pan  making  it  possible  to  adjust  the  size 
of  the  opening  to  the  size  of  the  vessel  to  be  heated. 
10  sets  Rings  for  water  baths,  in  sets.  Outside  diameter  of 
largest  ring  at  least  7  in. 


PRACTICAL  MANUAL 


173 


FIG.  14. 


FIG.  15. 


FIG.  16. 


FIG.  17.  FIG.  18.  FIG..  19. 


FIG.  20. 


FIG.  21. 


FIG.  22. 


174  CHEMISTRY  FOB  NURSES  AND  STUDENTS 


FIG.  23. 


FIG.  24. 


FIG.  25. 


FIG.  26. 


FIG.  27. 


FIG.  28. 


FIG.  29. 


FIG.  30.      FIG.  31. 


PRACTICAL  MANUAL 


175 


List  of  the  Elements,  their  Symbols,  Atomic  Weights, 
and  Valence. 

INTERNATIONAL  ATOMIC  WEIGHTS 

1920 


Name 

Symbol 

Atomic 
weight 

Principal 
valence 

Aluminum  ...              .                  .      . 

Al 

27  1 

3 

Antimony,  stibium 

Sb 

120  2 

3  or  5 

Argon 

A 

39  9 

o 

Arsenic  

As 

74  96 

3  or  5 

Barium 

Ba 

137  37 

2 

Bismuth 

Bi 

208  0 

3  or  5 

Boron  .    . 

B 

10  9 

3 

Bromine 

Br 

79  92 

1 

Cadmium  

Cd 

112  40 

2 

Caesium  

Cs 

132  81 

1 

Calcium 

Ca 

40  07 

2 

Carbon  

c 

12  005 

2  or  4 

Cerium  

Ce 

140  25 

4  or  3 

Chlorine 

Cl 

35  46 

1 

Chromium  
Cobalt 

Cr 
Co 

52.0 

58  97 

2,  3  or  6 
2  or  3 

Columbium,  niobium  

Cb 

93.1 

3  or  5 

CopDer.  . 

Cu 

63  57 

1  or  2 

Dysprosium 

Dy 

162  5 

3 

Erbium  

Er 

167.7 

3 

Europium  

Eu 

152  0 

3 

Fluorine 

F 

19  0 

1 

Gadolinium 

Gd 

157  3 

3 

Gallium  

Ga 

70.1 

3 

Germanium.  .                    ....        .    . 

Ge 

72  5 

4 

Glucinum  beryllium 

Gl 

9  1 

2 

Gold,  aurum  

Au 

197.2 

1  or  3 

Helium  

He 

4  00 

0 

Holmium 

Ho 

163  5 

3 

Hydrogen 

H 

1  008 

1 

Indium  

In 

114.8 

3 

Iodine     

I 

126  92 

1 

Iridium 

Ir 

193  1 

3  or  4 

Iro  n  f  errum                              , 

Fe 

55  84 

2  or  3 

Krypton  

Kr 

82.92 

0 

Lanthanum 

La 

139  0 

3 

Lead  plumbum 

Pb 

207  2 

2  or  4 

Lithium                                             « 

Li 

6  94 

1 

Lutecium  

Lu 

175.0 

3 

Magnesium  

Me 

24  32 

2 

Manganese  

Mn 

54  93 

2,  4,  6  or  7 

176 


CHEMISTRY  FOR  NURSES  AND  STUDENTS 


Name 

Symbol 

Atomic 
weight 

Principal 
valence 

Mercury,  hydrargyrum 

He 

200  6 

1  or  2 

Molybdenum 

Mo 

96  0 

3   4  or  6 

Neodymium  

Nd 

144  3 

3 

Neon  

Ne 

20  2 

o 

Nickel 

Ni 

58  68 

2  or  ^ 

Niton,  Ra  emanation  

Nt 

222  4 

Nitrogen  

N 

14  008 

3  or  5 

Osmium 

Os 

190  9 

2   3    4  or  8 

Oxygen  

o 

16  00 

2 

Palladium          

Pd 

106  7 

2  or  4 

Phosphorus 

p 

31  04 

3  or  5 

Platinum  \  

Pt 

195  2 

2  or  4 

Potassium,  kalium                                 , 

K 

39  10 

1 

Praseodymium  

Pr 

140  9 

3 

Radium  

Ra 

226  0 

2 

Rhodium 

Rh 

102  9 

3 

Rubidium  

Rb 

85  45 

1 

Ruthenium  

Ru 

101  7 

3  4  6  or  8 

Samarium 

Sa 

150  4 

3 

Scandium  

Sc 

44  1 

3 

Selenium  

Se 

79  2 

2  4  or  6 

Silicon 

Si 

28  3 

4 

Silver,  argentum  

Ae 

107  88 

1 

Sodium,  natrium  

Na 

23  00 

1 

Strontium 

Sr 

87  63 

2 

Sulphur 

s 

32  06 

2  4  or  6 

Tantalum  

Ta 

181  5 

5 

Tellurium 

Te 

127  5 

2  4  or  6 

Terbium  

Tb 

159  2 

3 

Thallium  

Tl 

204  0 

1  or  3 

Thorium 

Th 

232  15 

4 

Thulium                \.  . 

Tm 

168  5 

3 

Tin,  stannum  

Sn 

118  7 

2  or  4 

Titanium       ... 

Ti 

48  1 

3  or  4 

Tungsten  wolframium 

W 

184  0 

6 

Uranium 

u 

238  2 

4  or  6 

Vanadium  

V 

51  0 

3  or  5 

Xenon            .... 

Xe 

130  2 

0 

Ytterbium 

Yb 

173  5 

3 

Yttrium  

Yt 

89.33 

3 

Zinc  

Zn 

65.37 

2 

Zirconium.  .           

Zr 

90  6 

4 

INDEX 


Absorption  in  colon,  117 

of  fat,  influence  of  bile  on,  116 

of  starch,  125 

through  stomach  walls,  114 
Accuracy  in  laboratory  work,  143 
Acetates,  88,  89 
Acetic  acid,  86 

Acetone  derivatives  in  urine,  126 
Acetylene,  75 
Acid,  acetic,  86 

action  on  cotton,  142 
woolen,  142 

burns,  142 

butyric,    production   of    (De- 
monstration), 161 

chloric,  37 

chlorous,  37 

citric,  87 

hydrobromic,  37 

hydrochloric,  37 

hypochlorous,  37,  48 
use  in  bleaching,  49 

in  gastric  juice,  112 

lactic,  87 

nitric,  18,  37,  45,  62,  63,  142 

oleic,  90 

oxalic,  140 

palmitic,  90 

perchloric,  37 

phosphoric,  37 

radicles,  36 

salts,  38 

stearic,  90 

sulphuric,  37,  45.  142 

tartaric,  87 
Acidity,  35 
Acidosis,  126 

12  177 


Acids,  35 

amino,  105,  115,  122,  123 

as  catalysts,  89,  96,  104 

care  in  handling,  142 

dibasic,  40 

dicarboxylic,  87 

fatty,  90 

formation  by  bacteria,  86,  118 

formulae  of  common,  36 

in  vegetables  and  fruits,  140 

ionization  of,  43,  45 

monobasic,  40 

naming  of,  37 

necessary  in  the  diet,  46 

organic,  86,  87 

"strong,"  45 

study  of,  159 

tribasic,  40 

tricarboxylic,  87 

"weak,"  45 

Action  of  soap,  cleansing,  91 
Activation  of  pancieatic  juice,  116 

pepsin,  112 

trypsin,  116 

zymogens,  52 
Aerated  waters,  20 
"  Afterdamp,"  19 
Air,  "bad,"  54 

carbon  dioxide  in,  21 

monoxide  in,  19 

effect  of  overcrowding  on,  54 

in  motion  and  at  rest,  com- 
parative effects  of,  55 

inspired    and    expired    com- 
pared, 54 

necessary  amount  of  oxygen 
in,  54 


178 


INDEX 


Air,  nitrogen  in,  53 

organic  poisons  in,  55 

purification  by  ozone,    18 
Alcohol  in  uric  acid  disorders,  139 
Alcoholic  fermentation,  99 
Alcohols,  79,  84,  85,  86,  100 
Aldehydes,  83 

oxidation  of,  84,  86 

reactivity  of,  84 
Alimentary  glycosuria,  125 
Aliphatic  compounds,  76,  103 
Alkalies,  39 

action  on  wool,  142 

caustic,  39 

effect  on  skin,  142 

fixed,  39 

mild,  39 
Alkoxyl,  79 

Alkyl  groups,  77,  78,  102 
Allen  treatment  of  diabetes,  127 
Alloys,  70,  71 
Aluminium,  69 
Amino  acids,  105 

assimilation  of,  122 

comparative    importance    of, 
122,  123 

in  intestines,  115 

groups,  105 
Ammonia,  61 

action  on  copper,  69 

use  in  refrigerating  plants,  62 
Ammonium  carbonate,  39 

hydroxide,  39,  61 

salts,  61 

Amorphous  solids,  28 
Amyl,  77 
Amylases,  52,  97 
Amylolytic    enzymes     (See  amy- 


Amylopsin,  115 

Anaesthetics,   effect  on  blood,  132 

— ane,  termination,  78 

Anemia,  decrease  of  erythrocytes 

in,  133 

Anger,  effect  on  salivary  glands,  109 
stomach  glands,  111 


Animal  charcoal,  decolorization  of 
liquid     by     (Demonstra- 
tion), 153 
Anions,  44 
Anode,  43 
Anticipation,    effect    on    salivary 

glands,  109 
stomach  glands,  111 
Arginine,  105 
Aromatic  alcohols,  103 

compounds,  101,  103 
Arsenic  poisoning,  use  of  dyalized 

iron  in,  34 

Assimilation,  107,  121 
— ate,  termination,  37,  38 
Atmosphere,    carbon    dioxide    in, 

21 

monoxide  in,  19 
composition  of,  53 
effect  of  animal  life,  53 

plant  life,  54 
nitrogen  in,  53 
oxygen  in,  11,  53 
Atom,  4,  5 
Atomic  theory,  4 
weight,  5,  6 
weights,  table  of,  174 
Automatic  sprinklers,  71 


B 


Bacteria,  absorbed  by  leucocytes, 
135 

acid  forming,  118 

activity     in     purification     of 
water,  11 

B.  Bulgaricus,  119 

B.  Coli,  118 

formation  of  nitrates  by,  60 

in  digestive  tract,  118 

lactic  acid,  119 

putrefactive,  118 

souring  due  to,  86 
Baking  powder,  22 

soda,  21 
Barley,  81,  109 


INDEX 


179 


Bases,  38 

diacidic,  40 

ionization  of,  43,  45 

monacidic,  40 

"strong,"  45 

study  of,  159 

triacidic,  40 

"weak,"  45 
Baths,    increase    in    erythrocytes 

due  to,  133 
Battery,  electric,  42 
Beers,  81 
Benedict's    modification    of    Feh- 

ling  solution,  163 
Benzene,  102 

ring,  102,  103 

nucleus,  102 
Benzine,  76 
Beri-beri,  106 
Bi-,  prefix,  38 
Bile,  116 
Biose,  95 

Bleaching  powder,  49 
Blood,  131 

as  a  carrier,  131,  135 

clotting  of,  46,  131,  132,  168 

color  of,  133 

corpuscles,  26,  131 

defibrination,  168 

experiments  on,  168 

laking  of,  134,  168 

plasma,  26,  131 
Body  cells,  work  of,  122 

temperature,     regulation     of, 

55,  136 
Bonds,  9 

double  and  triple,  75 
Boring  corks,   147 
Bottles,  use  of  reagent,  143 
Brandy,  81 
Bromides,  49 
Bromine,  49 

burns,  141 

care  in  handling,  141 
Buchner,  99 
Bumping,  144 


Burning,  12 
Burns,  acid,  142 

alkali,  142 

bromine,  141 

phosphorus,  141 
Butter,  vitamines  in,  106 
Buttermilk,  119 
Butyl,  77 

Butyric  acid,  production  of    (De- 
monstration), 161 


Calcium  acid  carbonate,  92 
carbonate,  22 
hydroxide,  22,  39,  156 
ions,  influence  on  blood  clot- 
ting, 46,  132 
oxide,  22 

phosphate  in  the  diet,  47 
salts  in  the  clotting  of  blood, 

132 

in  hard  water,  92 
sulphate,  29 
Calorie,  128 
Calorimeter,  129 
Candles,  formaldehyde,  85 
Cane  sugar,  97 
Capacity,  estimation  of,  149 
Carbohydrate    content    of    blood, 

125 

body,  125 

diet,  effect  on  intestinal  putre- 
faction, 119 
from  protein,  124 
Carbohydrates,  95 

absorption  of,  124 
as  a  source  of  energy,  130 
assimilation  of,  124,  125 
digestion  in  mouth,  109 

stomach,  110 
excretion  of,  125 
experiments  on,  162 
fermentable,  98 
heat  of  combustion,  129 
reactions  of,  97 


180 


INDEX 


Carbohydrates,  storage  of,  125 

tests  for  constituents  in,  162 

time  retained  in  stomach,  114 
Carbolic  acid,  103 
Carbon  atom,  73 
Carbon  dioxide,  20 

action  on  lime  water,  21 

carried  by  blood,  135 

elimination,  measure  of,  129 

in  air,  54,  55 

solubility  of,  158 

study  of,  158 
Carbon  monoxide,  19 

combination     with     hemo- 
globin, 133,  134,  168 
Carbon  tetrachloride,  76 
Carbona,  76 

Carbonates  in  intestinal  juice,  115 
Carbonic  acid,  21,  37 

gas,  21 

Carbonyl  group,  84 
Carboxyl  group,  86 
Cardiac  portion  of  stomach,  110 
Care  in  handling  chemicals,  141 
Casein,  113 
Cast  iron,  66 
Casts,  setting  of,  29 
Catalyst,  manganese  dioxide  as  a 

(Demonstration),  160 
Catalysts,  50 

in  plant  and  animal  cells,  51 

in  saponification,  89 
Catalytic  agents  (See  catalysts) 
Cathode,  44 
Cations,  44 

Cellulose,  effect  on  peristalsis,  117 
Centigrade  and  Fahrenheit  scales 

compared,  153 
Charcoal  in  niters,  34 

decolorization     by     (Demon- 
stration), 153 
Charge,  electric,  41 

positive  and  negative,  42 
Chemical  energy,  16 

in  life  processes,  17 
in  muscles,  124 


Chemicals   requiring   special   care 

in  handling,  141 
Chewing  of  food,  109 
Chlorine,  48 
Chloric  acid,  37 
Chloroform,  76 
Chlorophyll,  16 
Chlorous  acid,  37 
Cholera,  effect  on  erythrocytes,  133 
Chyme,  113,  115 
Citric  acid,  87 
Cleansing  action  of  soap,  91 

the  skin  for  surgical  work,  82 
Clotting  of  blood,  131,  132,  168 

influence  of  calcium  ions  on, 

46 

Coagulation  of  suspensoids,  32 
fine  precipitates,  31 
protein,  ^166 

Coal  gas,  effect  due  to  carbon  mono- 
xide in,  134 
tar  products,  101 

Cobwebs,  use  to  stop  bleeding,  132 
Cod  liver  oil,  30,  106 
Collargol,  33 
Colloidal  solutions,  31 
Colloids,  32 
Colon,  117 

bacteria  in,  118 
Combining  power,  8 
Combustion,  12 
heat  of,  129 
of  a  candle  in  a  closed  space, 

53 
rate  at  different  temperatures, 

13 

spontaneous,  14 

Comparison    of    Fahrenheit    and 
Centigrade     scales     (De- 
monstration), 153 
Completeness  of  digestion,   114 
Components  of  a  mixture,   sepa- 
ration by  filtration,  150 
Compounds,  1,  2 

decomposition  into  elements, 
150 


INDEX 


181 


Compounds,  formation  of,  3,  149 

union  of  elements  in,  9 
Condenser,  30 
Conductor,  41 
Constipation,  117,  118 
Contractions  of  stomach  walls,  113 
Copper,  68 

action  of  ammonia  on,  69 

as  a  catalyst,  50 

polishes,  69 
Corks,  to  bore,  147 
Corn  syrup,  96 
Corpuscles,  26,  131,  132 

red  (See  erythrocytes) 

white  (See  leucocytes) 
Crystalline  solid,  28 
Crystallization,  28 

of  fibrin,  132 

water  of,  28 
Crystalloids,  32 

Cupric  oxide,  reduction  by  alde- 
hydes, 85 
Cuprous  oxide,  98 
Current,  electric,  41,  42 
Cutting  glass  tubing,  145 
Cystine,  105 


Dalton's  atomic  theory,  4 
Deaminization,  124 
Decantation,  washing  by,  152 
Decolorization  of  liquid  by  animal 
charcoal         (Demonstra- 
tion), 153 
Decomposition  of  compounds  into 

elements,  150 

Defibrination  of  blood,  168 
Deficiency  diseases,  106 
Denatured  alcohol,  80 
Dextrins,  97 
Dextrose,  96,  100,  109 
fermentation  of,  99 
in  blood,  124,  125 
muscles,  124,  125 
plasma,  131 
rapidity  of  assimilation,  125 


Diabetes,  126 

Allen  treatment  of,  127 
Diarrhea,   effect  on  erythrocytes, 

133 
Diastases,  52,  100 

in  saliva,  109 

action  on  starch,  97,  164 
Diastatic  enzymes  (See  diastases) 
Diet,  carbohydrate,  effect  on  intes- 
tinal putrefaction,  119 

in  diabetes,  126,  127 

in  uric  acid  disorders,  139,  140 

protein  in,  119,  123 

standard,  136,  137 
Diffusion,  24 
Digestibility,  114 
Digestion,  107 

completeness  of,  114 

ease  of,  114 

in  stomach,  110 

leucocytes  in,  135 

of  fat  by  gastric  juice,  113 

of  milk  in  the  stomach,  113 

of  protein  by  gastric  juice,  113 

of  protein  in  intestines,  115 

of  unappetizing  foods,  111 
Dilation  of  stomach,  111 
Dioxides,  12 

Disaecharides,  96,  97,  98 
Disodium  phosphate,  38 
Distillate,  31 
Distillation,  30 

'(Demonstration),  152 

Destructive,  3J 

Fractional,  30 
Distilled  water,  30 
Divalent  elements,  9 
Dogs,experirnents of  Pawlowon,  111 
Double  bonds,  75 
Drafts,  ill  effects  of,  57 
Drugs,         absorption         through 

stomach  walls,  114 
Dyalized  iron,  34 
Dyes,  101 

Dysentry,  effect  on  erythrocytes, 
133 


182 


INDEX 


E 


Ease  of  digestion,  114 
Efficiency  in  laboratory  work,  143 
Egg-white,     comparative    digesti- 
bility of  fluid  and  solid,  114 
hydrolysis  of  (Demonstration), 

167 

yolk,  vitamines  in,  106 
Electricity,  41 

positive  and  negative,  41,  42 
relation  between  valence  and, 

44 
Electrolytes,  43 

in  life  processes,  46 
Elements,  1,  2 

decomposition  of  compounds 

into,  150 
formation       of       compounds 

from,  150 

in  human  body,  3 

most  important,  2 

Emulsification  by  bile,  116 

theory  of  action  of  soap,  91 
Emulsions,  29 

temporary  and  permanent,  30 
Emulsoids,  32 
Enamelled  ware,  67 
Endogenous  uric  acid,  138 
Energy,  14 

chemical,  16,  17 

set  free  in  muscles,  124 
forms  of,  14,  15 
from  carbohydrates,  130 
fats,  130 
proteins,  130 
indestructibility  of,  14 
measured  in  calorimeter,  130 
of  animals,  17 
combination,  15 
life  processes,  16 
ozone,  18 

sun,  utilized   by  plants,  16 
storage  of  by  plants,  17 
transformation  of,    14,   128 
value  of  food,  128,  129,  130 


Enterokinase,  115 
Enzymes,  51 

classification  of,  52 
fermentation  by,  98 
hydrolysis     of     carbohydrate 

by,  96,  97 
protein  by,  104 
in  barley,  109 
gastric  juice,  112 
intestines,  115 
saliva,  109 

of  liver,  action  on  fats    (De- 
monstration), 160 
saponification  by,  89 
Equations,  7 

Equilibrium  between  ions  in  solu- 
tion, 44 
Erepsin,  115 
Erythrocytes,  132 

affinity  for  oxygen  decreased 
by  carbon  monoxide, 
135 

area  in  man,  134 
effect  of  iron  salts  on,  133 
Esters,  89 
Estimation  of  temperature,  145 

capacity,  149 
Ether  as  a  solvent,  82 
an  anaesthetic,  82 
care  in  handling,  142 
Ethers,  81 
Ethyl,  77 

acetate,  89 
alcohol,  80 

oxidation  of,  86 
benzene,  102 
Ethylene,  75 

Evaporation,  31,  62,  151 
Excitement,     effect     on     salivary 

glands,  109 
stomach  glands,  111 
Excretion  of  sugar,  125,  126 
Exercise,    effect   on   carbohydrate 

content  of  body,  125 
Exogenous  uric  acid,  138 
Explosives,  63,  101 


INDEX 


183 


Exposure,  effect  on  carbohydrate 
content  of  body,  125 

Extractives  of  food,  111 
barley  grain,  81 


Fahrenheit  and  Centigrade  scales, 
comparison  of     (Demon- 
stration), 153 
Family  of  elements,  48 
Fasting  treatment  of  diabetes,  127 
Fats,  90 

absorption  of,  116 

action    of    liver   enzyme   on 

(Demonstration),  160 
as  source  of  energy,  130 
assimilation  of,  121 
butyric   acid   from     (Demon- 
stration), 160 
digestion  in  stomach,  113 

intestines,  115 
effect  on  acidosis,  126 
experiments  on,  161 
functions  of,  121 
heat  of  combustion,  129 
hydrolysis  of,  91 
test  for  glycerine  in,  161 
time  retained  in  stomach,  114 
Fatty  acids,  action  of  bile  on,  116 
substances  in  plasma,  131 
tissue,  121,  122 
Feces,  136 
Fehling  solution,  98 

Benedict's     modification     of, 

163 
test  for  glucose,  163 

sugar  in  urine,  125 
Fermentation,  80,  98,  99,  100,  164 
production  of  carbon  dioxide 

in,  20 

Ferments,  51 
Ferric  chloride,  38 
Ferrous  chloride,  38 
Fertilizers,  59 
Fibrin,  131 


Filter  paper,  folding,  145 

Filters,  charcoal,  34 

Filtration,  31,  150 

Fire  extinguishers,  use  of  carbon 

dioxide  in,  20 

Fires,  formation  of  carbon  mono- 
xide in,  19 

lighting  of,  13 
Fish,  purines  in,  139 
Flavoring  extracts,   101 
Folding  filter  paper,  145 
Food  materials  carried  by  blood, 

131 

Food-stuffs,  108 
Formaldehyde,  85 
Formalin,  85 
Formates,  89 
Formation    of    compounds    from 

elements,  149 
Formulse,  7 

calculation   of  valence  from, 
10 

graphic  or  structural,  74 

order  of  elements  in,  8 

writing  of,  10 
Fundus,  110 
Fusible  metal,  71 
Fusion  mixture,  165,  167 
Fructose,  96,  100 
Fruit  sugar,  96 
Fruits  in  the  diet,  46 


Gain  in  weight  when  substances 
are  oxidized  (Demons- 
stration),  154 

Galactose,  96 

Gall-stones,  116 

Galvanized  iron,  67 

Galvanometer.  42 

Gasoline,  76 

care  in  handling,  142 

Gastric  juice,  110,  112 

antiseptic  effect,  119 

Gauze,  dissipation  of  heat  by,  13 


184 


INDEX 


Gelatine,  as  supplementary  food, 
123 

effect  in  ice-cream,  33 
General  directions  for  laboratory 

work,  143 
Gies  reagent,  166 
Glands,  parotid,  108 

salivary,  108 

sebaceous,  136 

stomach,  111 

sublingual,  108 

submaxillary,  108 
Glass  tubing,  bending,  146 

cutting,  145,  147 
Glucose,  96,  97 

as  food,  126 

Fehling  solution  test  for,  163 
Glue,  setting  of,  33 
Glycerine,  79,  90,  91 

in  fat,  test  for,  161 
Glycine,  105 
Glycogen,  124 

in  liver,  124,  125 

muscles,  124 
Glycosuria,  125 
Gold,  64 

Gouty  symptoms   cause  of,  138 
Grape  sugar,  9 
Graphic  formulae,  74 
"Gravel,"  138 

Green  plants,  production  of  oxy- 
gen by  (Demonstration), 
154 

Group  of  atoms,  8 
Growth-promoting         substances, 

106,.  108 

Gruel  in  milk,  effect  of,  33 
Gum  arabic,  effect  in  candy,  33 
Gun  powder,  18 
Gypsum,  29 


Halides,  48 
Halogen  family,  48 

substitution  products,  76 
Handling  chemicals,  care  in,  141 


Hard  soap,  91 

water,  92 

Headaches,  chronic,  118,  139 
Heart  beat,    influence   of   certain 
ions  on,  46 

strain  caused  by  fatty  tissue, 

121 

Heat  change  hi  chemical  reactions, 
3,  16 

effect  of  accumulation  in  the 
body,  55 

loss  from  the  body,  55 

by  evaporation,  55,  62 
radiation,  56 

of  combustion,  129 

production  in  the  body,  55 
Heating  liquids,  143,  144 

test  tubes,  143,  144 
Hemoglobin,  17,  133 

combination  of  carbon  mono- 
xide with,  19,  133 

reactions  of,  168 
Hemolysis,  134 
Hemophilia,  132 

Hemorrhage,  clotting  of  blood  in, 
132 

storage  of  protein  after,  123 
Heptyl,  77 
Hexoses,  95 
Hexyl,  77 

Homologous  series,  78 
Humidity,  56 
Humus,  33 
Hydro-,  prefix,  37 
Hydrobromic  acid,  37 
Hydrocarbons,  75,  102 
Hydrochloric  acid,  37 

in  gastric  juice,   112 

ionization  of,  45 
Hydrogen  peroxide,  22 
Hydrolysis,  of  carbohydrates,  96, 
97,  99,  100,  115 

casein,  113 

esters,  89 

fats,  91,  113,  115 

Demonstration),  161 


INDEX 


185 


Hydrolysis,  of  glycogen,  124 

proteins,  104,  112,  115 

starch,  97,  125 
Hydroxides,  8,  39 

distribution  of  valences  in,  9 
Hydroxyl  group,  9,  39 

in  alcohols,  79,  86 

aromatic  compounds,  103 

valence  of,  9 
Hyper-,  prefix,  37 
Hyperacidity  of  gastric  juice,  112 
Hypertonic  solutions,   26 
Hypo-,  prefix,  37 
Hypoacidity  of  gastric  juice,  112 
Hypochlorous  acid,  37,  48 

use  in  bleaching,  49 
Hjrpotonic  solutions,  26 


I 


Iron,  66 

galvanized,  67 
in  hemoglobin,  133 
Irritability  of  muscles,  influence  of 

sodium  salts  on,  46 
Isodynamics,  law  of,  130 
Isomers,  75 

Isomerism  in  the  alcohols,  81 
carbohydrates,  95 
hydrocarbons,  74 
Isotonic  solutions,  26 
ite,  termination,  37 


Jaundice,  116 
Juice,  gastric,  110 
intestinal,  115 
pancreatic,  115 
Junket,  113 


ic,  termination,  37 

— ide,  termination,  37 
Indole  ring,  105 

Influences,    chemical   on   stomach 
glands,  11,   112 

psychical,  on  salivary  glands, 
109 

stomach  glands,  111 
Insoluble  substances,  27 
Insulators,  41 
Intestinal  glands,  115 

juice,  115 
Intestine,  large,  117 

small,  114 
Invertase,  100 
Invertin,  115 
Iodine,  49 

tincture  of,  49 
lodoform,  76 
Ionic  theory,  43 

lonization,  factors  influencing,  44 
Ions,  43 

properties  due  to,  45 

influence  on  osmotic  pressure 
of  body  fluids,  46 


Kerosene,  76 
Ketones,  84 

oxidation  of,  85,  86 
Kidney,  purines  in,  139 
Kindling  point,  13 

use  in  lighting  fires,  14 


Laboratory    work,    general    direc- 
tions for,  143 

Lactase  in  intestinal  juice,  115 
Lactic  acid,  87 

bacteria,  119 
Lactose,  97 
Lsevulose,  96 
Laking  of  blood,  134,  168 
Large  intestine,  117 
Law  of  isodynamics,  130 
Lead,  69 

action  of  water  on,  70 
Leucine,  105 

crystallization  of,  167 
Leucocytes,  134,  135 
Leucocytosis,  135 


186 


INDEX 


Life  processes,  energy  set  free  in,  17 

stored  in,  17 

oxidation  and  reduction  in,  18 
Lime  water,  22 

action  of  carbon  dioxide  with, 

21 

preparation  of,  156 
Linseed  oil,  action  in  paint,  14 
Lipases,  52 

in  gastric  juice,  112 
Lipolytic  enzymes,  (See  lipases) 
Liquid,  decolorization  by   animal 
charcoal         (Demonstra- 
tion), 153 

Liquids,  heating,  143 
Lithemia,  139 
Litmus,  35 

action  with  acids,  35 

bases,  38 
Liver,  116 

dextrose  in,  124 
enzyme,  action  on  fats    (De- 
monstration), 160 
glycogen  in,  124,  125 
metabolism  of  carbohydrates 

in,  124,  125 
purines  in,  139 
Lunar  caustic,  65 
Lungs,  excretion  through,  136 
Lymph  vessels,  121 


M 


Magnesium  salts  in  hard  water,  92 
Maize  as  source  of  protein,  123 
Maltase,  100 

in  intestinal  juice,  115 

saliva,  109 

Maltose,  97,  109,  115 
Malt  sugar,  97 
Manganese  dioxide  as  a  catalyst 

(Demonstration),  160 
Massage,  increase  in  erythrocytes 

by,  133 

Mastication,  109 
Matches,  use  in  lighting  fires,  13 


Meat,  purines  in,  139 
Mechanical  energy  of  muscles,  124 
Membrane,  mucous,  110 
Mercuric  chloride,  38 
Mercurous  chloride,  38 
Metabolism,  107 

estimation  in  calorimeter,  129 
Metal,  35,  64 

symbols  for  common,  36 
Metallic  oxides,  reduction  of,  98 
Metchnikoff,  118 
Methane,  73 
Methyl,  77 

acetate,  89 

alcohol,  79 
Metlwlated  spirit,  80 
Milk,  as  supplementary  food,  123 

leg,  132 

of  lime,  157 

souring  of,  87 

sugar,  97 

test  for,  165 
Millon's  reagent,  166 
Miner's  lantern,  13 
Mixed  fats,  90 
Mixtures,  definition  of,  3 
Molecular  weight,  6 
Molecule,  4,  5 
Monobasic  acids,  40 
Monohydric  alcohols,  79 
Monosacchaiides,  96 

absorption  of,  124 
Monosodium  phosphate,  38 
Monovalent  elements,  9 
Mucous  membrane,  110 
Muscles,  energy  in,  124 

glycogen  in,  124 

influence  of  sodium  salts  on 

irritability  of,  46 
Mycoderma  aceti,  86 

N 

Neatness  in  laboratory  work,  143 
Neutralization,  39,  45,  160 
of  organic  acids,  87 
chyme,  115 


INDEX 


187 


Nickel,  68 
Nitrates,  37 

formation  by  bacteria,  60 

importance  in  plant  life,  59 
Nitric  acid,  37,  62 

as  oxidizing  agent,  18,  63 

burns,  142 

ionization,  45 
Nitrites,  37 
Nitrogen,  53 

assimilation  by  animals,   59, 

106 
plants,  59,  106 

compounds  in  plasma,  131 

cycle,  60 

fixation  of,  60 

in  protein,  test  for,  165 

protein  a  source  of,  106 
Non-conductors,  41 
Nonoses,  95 
Normal  saline,  2/ 
Nucleus,  benzene,  102,  103 


O 


Oats,  as  a  source  of  protein,  123 

Octyl,  77 

Oil,  paint,  14 

Old  age,  118 

Oleate,  90 

Oleic  acid,  90 

Opsonic  index,  135 

Opsonins,  135 

Organic  chemistry,  73 

Osmosis    (Demonstration),    157 

Osmotic  pressure,  25 

of  blood  corpuscles,  26,  27 

body  fluids,  due  to  ions,  46 

ous,  termination,  37 

Overcrowding,  effect  of,  54 
Oxalic  acid  in  vegetables,  140 
Oxidation,  12,  17 

gain  in  weight  during    (Dem- 
onstration), 154 

of  alcohols,  83,  84,  86 
aldehydes,  84,  86 


Oxidation  of  ketones,  85,  86 
food  in  the  body,  120 
rise  in  temperature  during,  14 
Oxides,  12 

cupric,  98 
cuprous,  98 

metallic,  reduction  of,  98 
of  carbon,  19 
of  hydrogen,  22 
Oxidizing  agents,  18 
Oxygen,  11 

activity  in  atmosphere,  11 
carried    by    hemoglobin,    17, 

133 
importance    to    aquatic    life, 

11 
in  purification  of  water,  11 

blood,  17,  133 
production  by  green   plants 

(Demonstration),  154 
susceptibility  of  metals  to,  11, 

65,  66,  68,  69 
used  in  metabolism,  129  " 
Oxyhemoglobin,  17,  133 
Ozone,  18 
Ozonizers,  18 


Palmitate,  90 
Palmitic  acid,  90 
Pancreas,  115 
Pancreatic  juice,  115 
Paracasein,  113 
Paraffins,  76 
Paraformaldehyde,  85 
Parotid  gland,  108 
Pawlow,  111 
Pepsin,  52,  112 
Peptones,  112 

action  of  erepsin  on,  115 
Per-,  prefix,  37 
Perchloric  acid,  37 
Perfumes,  101 
Peristalsis,  117 


188 


INDEX 


Permanent  hardness,  93 

Perspiration,  136 

Petroleum  ether,  care  in  handling, 

142 

Phenols,  103 
Phenyl  radicle,  102 
Phosphates,  37 
Phosphites,  37 
Phosphoric  acid,  37 
Phosphorus,  care  in  handling,  141 

burns,  141 

Physiological  saline,  27 
Plants,  production  of    oxygen  by 

(Demonstration),  154 
Plasma,  131 
Plaster-of-Paris,  29 
Plasmolysis,  26 
Platinum,  64 

as  a  catylist,  50 
Pneumonia,  uric  acid  excretion  in, 

138 

Poisoning,  arsenic,  use  of  dyalized 
iron  in,  34 

coal  gas,  134 

lead,  70 

ptomaine,  118 

Poisons,        absorption        through 
stomach  walls,  114 

carbon  monoxide,  19,  134 

copper  salts,  68 

lead  salts,  70 

production     by     putrefactive 
bacteria,  118 

verdigris,  68 
Poles,  electric,  42 
Polyhydric  alcohols,  79 
Polysaccharides,  97,  98 
Potassium,  acetate,  88 

care  in  handling,  141 

hydroxide,  39 
ionization  of,  45 

sulphate,  38 
Primary  alcohols,  81 
oxidation  of,  83 

phosphates,  38 
Propionates,  88 


Propyl,  77 

alcohol,  81 
Proteases,  52,  109 
Proteins,  59,  104 

acetone  bodies  from,  126 
action  of  pepsin  on,  112 
saliva  on,  109 
trypsin  on,  115 
as  a  source  of  energy,  124,  130 
coagulation  of,  166 
digestion  in  intestines,  115 
heat  of  combustion  of,  129 
hydrolysis     of      (Demonstia- 

tion),  167 
in  diet,  excess  of,  123 

effect  in  intestinal  putrefac- 
tion, 119 
variation  in,  123 
plasma,  131 
of  blood,  131 
sugar  from,  126 
storage  of,  123 
tests  for  constituents  in,  165 

on,  165 

time  retained  in  stomach,  114 
Proteolytic     enzymes     (See     pro- 


Pro  teoses,  112 

action  of  erepsin  on,  115 
Psychic     influences     on     salivary 

glands,  109 
stomach  glands,  111 
Ptomaine  poisoning,  118 
Ptyalin,  109,  110 
Purines,  138 

foods  rich  in,  139 
Putrefaction,  old  age  due  to,  118 
Putrefactive  bacteria,  118 
Pyloric  portion  of  stomach,  110 
Pylorus,  110 

opening  and  closing  of,  113 
Pyridine  bases,  80 


Quicklime,  22 


INDEX 


189 


R 


Radicles,  acid,  36 

alkyl,  77 

phenyl,  102 
Reagent,  biuret,  166 

bottles,  use  of,  143 

Gies  (See  biuret) 

Millon's,  166 

Stokes/  168 
Reducing  agents,  18 

aldehydes  as,  85 
Reduction,  17 

Regulation   of  carbohydrate   con- 
tent of  blood,  125 

temperature,  55,  56,  136 
Rennet  (See  rennin) 
Rennin,  112,  113 
Repair  of  tissues,  107,  122 
Ring,  benzene,  102 
Ringer's  solution,  27 
Rivers,  sewage  in,  11,  33 

muddy,  33 

Rubber  stoppers,  to  put  on  glass, 
147 

tubing,  to  put  on  glass,  147 
Rum,  81 
Rusting  of  iron,  66 


3 


Saline,  normal  or  physiological,  27 

Saliva,  108, 109,  110 

action  in  stomach,  110 

Salivary  glands,  108 

"Salt,"  35 

definition  of,  35,  36 

Saltpetre,  an  oxidizing   agent,    18 

Salts,  as  food  stuffs,  108 
in  saliva,  109 
plasma,  131 
ionization  of,  43,  45 
naming  of,  37,  88 
of  organic  acids,  87,  88 
present  in  hard  water,  92   • 
reactions  due  to  ions,  45 
"smelling,"  61 


Saponification,  89 
Saturated  hydrocarbons,  75,  102 
Scale  in  kettles,  93 
Scurvy,  106 
Sebaceous  glands,  136 
Secondary  alcohols,  81 
oxidation  of,  84 

phosphates,  38 
Secretin,  115 
Secretion  of  intestinal  glands,  115 

livei,  116 

pancreas,  115 

salivary  glands,  108 

sebaceous  glands,  136 

stomach  glands,  110,  113 
Secretions    carried  by  the  blood, 

131 

Semipermeable  partitions,  25 
Separation  of  mixtures  into  com- 
ponents, 31,  150,  152 
Series,  homologous,  78 
Serum,  131 
"Setting"  of  casts,  29 

glue,  jelly,  etc.,  32 
Sewage,  colloidal  material  in,  33 

effect  of  bacteria  on,  11 

faims,  34 

Side  chains,  102,  103 
Silver,  64 

action  of  vinegar  on,  66 

nitrate,  65 

plating  powders,  66 

polishes,  65 

''sterling,"  66 

Skin,  cleansing  for  surgical  work, 
82 

excretion  through,  136 
Small  intestine,  114 
Smelling  salts,  61 
Soap,  91 

action  with  hard  water,  92 

preparation  of,  161 

tests  on,  161 
Soaps,  formation  in  the  intestines, 

115 
Soda  water,  20 


190 


INDEX 


Sodium  acetate,  88 

bicarbonate,  administration  in 
acidosis,  126 

carbonate,  38,  39 
in  blood,  135 

care  in  handling,  141 

chloride,  38 

hydroxide,  39 

phenolate,  103 
Soft  soap,  91 
Softening  of  water,  92 
Soil,  humus  in,  33 

purification  of  water  by,  34 
Solder,  70 
Solubility,  factors  governing,  27 

of  calcium  hydroxide,  27 

carbon  dioxide,  20,  21 

gases,  28 

oxygen,  11 

sodium  chloride,  27 
Solute,  24 
Solution,  24,  156 

colloidal,  31 

Fehling,  98 

of  sulphuric  acid  in  water,  142 

saturated,  28 
Soup  as  an  appetizer,  111 
Souring,  86 
Spongy  platinum,  50 
Sprinklers,  automatic,  71 
Standard  diet,  136,  137 
Starch,  97,  100 

absorption  of,  125 

action  of  diastase  with,  164 
saliva  on,  109 

tests  with,  163 
Steapsin,  115 
Stearate,  90 
Stearic  acid,  90 
Steel,  66 

"Sterling"  silver,  66 
Still,  30 

Stimulation  of  salivary  glands,  108, 
109 

stomach  glands,  111 

pancreas,  115 


Stimulation  of  peristalsis,  117 
Stokes  reagent,  168 
Stomach,  110 

action  of  saliva  in,  110 

contractions  of,  113 

dilation  of,  111 
Stoppers,  rubber,  to  put  on  glass, 

147 

Storage  of  fat,  121 
"  Strong "  acids  and  bases,  45 
Structural  formulse,  74 
Styrene,  102 
Sublingual  gland,  108 
Submaxillary  gland,  108 
Sucrose,  97 

Suet,  vitamines  in,  106 
Sugar,  excretion  of,  125,  126 

as  a  stimulant,  127 

in  milk,  test  for,  165 
Sulphates,  37 
Sulphites,  37 
Sulphur     in     protein,     test     for, 

165 
Sulphuric  acid,  37 

care  in  handling,  142 
ionization  of,  45 

ether,  82 
Surface  of  colloids,  34 

charcoal,  34 

Surfaces,  attraction  between,  34 
Surgical  work,  cleansing  the  skin 

for,  82 
Suspensions,  29 

filtering,  31 

of  clay,  33 
Suspensoids,  32 
Sweetbreads,  139 
Symbols,  6 

tables  of,  174 


Table  of  atomic  weights,  symbols, 

and  valences,  174 
Tar,  coal,  101 


INDEX 


191 


Tarnishing  of  silver,  65 
Tartaric  acid,  87 
Tartrates,  88 

Teeth,  function  in  digestion,  108 
Temper  of  steel,  66 
Temperature,  effect  of  changes  of, 
57 

estimation  of,  145 

influence  on  solution,  27 
enzyme  action,  51 

regulation,  55,  56,  136 

standard  for  rooms,  56 
Temporary  hardness,  93 
Tertiary  alcohol,  81 

oxidation  of,  84 

phosphates,  38 
Test  tubes,  heating,  143 
Tetravalent  carbon,  73 
Tetrose,  95 
Theory,  atomic,  4 

ionic,  43 

of  action  of  soap,  91 
Tin  cans,  leaving  food  in  open,  70 
Tincture  of  iodine,  49 
Tissues,  repair  of,  107 

fatty,  121,  122 
Tolerance  for  food  stuffs,  127 
Toluene,  102 

Transformation  of  energy,  128 
Tribasic  acids,  40 
Tricarboxylic  acids,  87 
Triose,  95 
Trioxides,  12 
Triple  bonds,  75 
Tiisodium  phosphate,  38 
Trivalent  elements,  9 
Trypsin,  52,  115 

activation  of,  116 
Tryptophane,  105 
Tubing,  glass,  bending,  146 
care  in  handling,  147 
cutting,  145,  147 

rubber,  to  fit  on  glass,  147 
Tyrosine,   105 

crystallization  of,  167 


IT 


Ultramicroscope,  2,  32 
Unappetizing    food,    digestion    of, 

111,  112 

Unsaturated  hydrocarbons,  75,  102 
Unslaked  lime,  22 
Uric  acid,  138 

disorders,  138,  139 
Urine,  137 

acetone  derivatives  in,  126 
examination  of,  137 
excretion  of  nitrogen  in,  124, 

137 

test  for  sugar  in,  98,  125 
uric  acid  in,  138 


Valence,  8 

of     common     elements     and 
groups,  10 

positive  and  negative,  8 

relation    between     electricity 
and,  44 

representation  of,  9 

use  in  writing  formulae,  10 

variable,  10,  38 
Valences,  tables  of,  174 
Vegetables  in  the  diet,  46 

effect  of  copper  on,  68 

purines  in,  139 

oxalic  acid  in,  140 
Velocity  of  reactions,  13 
Ventilation,  window,  57 
Verdigris,  68 
Vinegar,  87 

action  on  silver,  66 
Vitarnines,  106,  108 


W 


Walls   of   intestines,    contractions 

of,  117 
passage  of  fats  through,  121 


192 


INDEX 


Wall  of  intestines,  production  of      Water,  solubility  of  carbon  dioxide 


secretin  by,  115 
stomach,  110 

absorption  through,  114 
contractions  of,  113 
Wash  bottle,  148 
Washing  by  decantation,  152 

soda,  93 
Waste  material,  carried  by  blood, 

131 

excretion  of,  136 
Water,         absorption         through 

stomach  walls,  114 
aerated,  20 
a  non-conductor,  42 

as  a  catalyst,  50  < 

dissolved  oxygen  in,  11 

elimination,  measure  of,  129         Xylene,  102 
hard,  92 

influence  on  ionization,  44 
in  saliva,  109 
proportion     of     oxygen     by      Yeast,  98,  99 

weight,  8 
volume,  8 
purification  by  bacteria,  11 

ozone,  18  Zymase,  99,  100 

separation  into  elements,  2,  15      Zymogens,  51 
soda,  20  pepsin,  112 


in,  20 
gases  in,  11 

"Weak"  acids  and  bases,  45 
Weight,  gain  when  substances  are 

oxidized,  154 

Wheat,  as  a  source  of  protein,  123 
Whiskey,  81 

distilling,  30 
Wines,  81 
Wood,  destructive  distillation,  80, 

87 

spirit,  79 
Wrought  iron,  66 


OVERDUE. 


16Nlay'56L 
2-1956C1 


YB   16935 


IVERSITY  OF  CALIFORNIA  LIBRARY 


